What is WBGT ?

Guest Essay by Kip Hansen — 10 September 2023

Despite recent findings that unusually cold temperatures cause far more deaths than unusually warm temperatures, The Washington Post and an outfit called CarbonPlan have launched a project that:  “used new models and massive data sets to produce the most up-to-date predictions of how often people in nearly 15,500 cities would face such intense heat that they could quickly become ill — in the near-term and over the coming decades. The analysis is based on a measure called wet-bulb globe temperature (WBGT), which takes into account air temperature, humidity, radiation and wind speed, and is increasingly used by scientists to determine how heat stresses the human body.” [ source ]  

The Washington Post piece uses Pakistan and its “hottest place on Earth” as the poster child-like example for how climate alarmists think that extremely high  temperatures caused by  “climate change” will “kill kill kill” [h/t Alice’s Restaurant Massacree by Arlo Guthrie].  Of course, the Post perpetuates the disinformation that 1/3 of Pakistan was underwater [ and here ] from flooding in 2022, with the reality having been around 8-10% at the highest water levels, which quickly receded in most places.  Of course, the flooding caused by the extra-strong 2022 Monsoon Rains overwhelmed the nascent flood control efforts of Pakistan, which is a very poor country with infrastructure still fighting its way out of the “primitive” classification.  It was a true disaster for the people of Pakistan some who are still struggling to recover.

But it is not the heat that is killing the rural poor in Pakistan, it is the diseases that come from and with poverty and lack of health care infrastructure.

Of course, with large areas left with stagnant ponds and puddles, malaria ramped up as it does every monsoon, but more so.    The flooding had nothing to do with “climate change” – it was a fairly common stronger monsoon but with even more rain.  These stronger monsoons predictably cause flooding in Pakistan – and there were massive floods in 1950, 1992, 1993, 2010, and 2022.  The cause of the flooding, according to a recent paper in Nature-Scientific Reports“In August 2022, one of the most severe floods in the history of Pakistan was triggered due to the exceptionally high monsoon rainfall.” 

The more  interesting thing that comes up in this Washington Post article is  that: “To document one of the most widespread threats — extreme heat — The Post and CarbonPlan, a nonprofit that develops publicly available climate data, used new models and massive data sets to produce the most up-to-date predictions of how often people in nearly 15,500 cities would face such intense heat that they could quickly become ill — in the near-term and over the coming decades. The analysis is based on a measure called wet-bulb globe temperature (WBGT), which takes into account air temperature, humidity, radiation and wind speed, and is increasingly used by scientists to determine how heat stresses the human body.

The Post defined its dangerous heat threshold as more than 89.6°F wet-bulb globe temperature, claiming that this was equal to a temperature of 120 degrees on a dry day, or mid-90s temperature on a very humid day.   A WBGT over 89.6°F is the level at which there should be no strenuous outside work or exercise in the direct Sun, with the “flag” system, that index rating is Black Flagged by most organizations (see the charts far below).   But, this is how this 70-year-old index will be misused to create and spread fear and panic about “global warming” – making direct comparisons between the WBGT Index and Thermometer Temperatures, using an unfamiliar index value that is little understood by the public, and computationally inventing future WBGT readings.   

In order to show why this effort to create wide -area of global maps of future WBGT is simply impossible, I’ll have to explain what WBGT is when it leaps out of bed in the morning.

So, what exactly is Wet-Bulb Globe Temperature?  “The wet-bulb globe temperature (WBGT) is a type of apparent temperature used to estimate the effect of temperature, humidity, wind speed (wind chill), and visible and infrared radiation (usually sunlight) on humans.”  This “apparent temperature” (calculated in F or C) is not a temperature at all, but rather just a value – a number – an index — that can be shown as a scale and given as a scale of potential heat stress that might be experienced in direct Sun and strenuous human activity  — think, construction work,  agricultural laborers or a high school sports team during afternoon football or soccer practice.  This index was originally developed in the 1950s by the U.S. military to reduce heat stress deaths during military training exercises. WBGT is intended to be used as a guide to managing workload stress in direct sunlight. Another version of WBGT can be used indoors by ignoring some of the elements used to calculate it (wind speed, and “visible and infrared radiation (usually sunlight).”

The problem then became:  ”However, recently the National Weather Service (NWS) was asked to provide the WBGT using only data that is routinely collected by the NWS. The main problem with this is that one of the variables in the equation to calculate WBGT is the “globe temperature.” This temperature is found by using a copper globe painted in black matte paint with a thermometer inserted so that the bulb is in the center of the globe. This temperature is not routinely collected by the NWS.”    To overcome this problem:  “This paper shows how the globe temperature can be approximated using only data routinely collected by the NWS. A fourth degree polynomial equation is derived for globe temperature with the coefficients dependent on readily available data. Then, it is shown that the fourth-degree polynomial can be reasonably approximated by a linear equation, thus making computation less costly and time-consuming.

Here, like many other calculated metrics, there is some unfortunate naming.  Let’s look at the name:  Wet-Bulb Globe Temperature.

Wet-Bulb:  refers to “wet-blub temperature”, one of the inputs into the formula for determining WBGT.  This is an actual temperature measurement, in degrees, F or C.

Globe Temperature:  This is more correctly “black globe temperature”. “Black globe temperature is measured with a thermometer inside a black globe, which indicates how hot it feels in direct sunlight.” [ source ] This is also an actual temperature measurement, in degrees, F or C, albeit inside of a black painted metal globe.  It is used as a substitute for direct measurement of “visible and infrared radiation (usually sunlight)”.

However, WetBulb Globe Temperature (WGBT) is not a temperature at all – the words “global” and “temperature” are together as “globe temperature” – and the whole aconymed down to Wet Bulb Globe Temperature thus to WGBT — however, WBGT is an index.   Just a number that can be compared only to other numbers of the same index.  It is not a measure of sensible heat.  When the WBGT is reported, it is given in WBGT(F) or WBGT(C), like this “86.7˚F” which looks like, but is not, a temperature.  The “˚F” means nothing more than the WBGT was calculated using degrees Fahrenheit.  (similarly for ˚C).

To accurately measure the WBGT index for a particular place and time, one needs a set-up something like the one below, which is, if you look closely, two or three systems being compared:

On the mic-stand (middle) is a stand-alone Kestrel 5400 WBGT meter couple with a wind vane to turn the anemometer to the wind.   The Kestrel system approximates the WBGT closely enough for safety purposes.  We can see (mostly) the needed elements: air temperature, humidity (directly or via a wet bulb thermometer), radiation (black globe) and wind speed.

Just yesterday, I demonstrated the principles of WBGT to myself (I took time off from this research project to help my son paint a local widow’s concrete front porch on a 90°F day, in the hot direct sun.)  It is very humid where I live,  with the relative humidity over 90% almost every day during the summer.   If I stood in the sun near the garage,  even with its door open to prevent reflected solar radiation,  I quickly became overheated.  If I moved just 20 feet down the driveway, where a gentle breeze was blowing up the street, I immediately felt cooler, felt comfortable.  This is why wind speed is included in the full WBGT calculation.   This practical experiment convinced me of the validity of the WBGT index and also that WBGT is extremely dependent on specific very-local conditions – local within feet or yards/meters,  but not kilometers or miles, not degrees of longitude and latitude. 

Here are scales from weather.gov, with their flag colors:

[ Open larger image in new tab ]

It is interesting to note that the hotter and more humid parts of the country, Region/Category 3 (dark grey) have higher allowable WBGT index readings and the cooler, less humid regions have lower allowable index readings.

The Washington Post and CarbonPlan produce an advanced globe graphic claiming to show “Number of days in 2030 with highly dangerous heat in the sun” (using WBGT as the determining factor) for cities all over the world.  I cannot reproduce the graphic here, but please follow the link to see the Post article, the rotating globe graphic is about halfway down.    They use the miracle of supercomputers to produce knowledge about the future. 

Can the method used by CarbonPlan possibly produce reliable and accurate estimates of WBGT heat stress, even for the past based on available data, no less for the future? Quickly glance down the linked  methods page and count the number of assumptions, guesstimates, default values, fudge-adjustments and … it is far too long and complex to include here.     Ridiculous!  I don’t think it stands any chance producing anything even vaguely accurate at all.  It is no better than saying:  “It gets hot and muggy in Louisiana in the summertime.”  And the same for Bangalore.

To give yourself an example of what is needed to determine the WBGT for a single location and time, visit OSHA’s WBGT CalculatorThe calculator asks for the following information:  the precise day and time, to the minute; time zone (for the time given); latitude; longitude; dry bulb air temperature; relative humidity; wind speed (in mph); barometric pressure (in inches of Hg); wet bulb temperature (uses a default value if unknown);  solar irradiance (W/m2) (uses  default if unknown).  Using data from a National Estuarine Research Reserve System weather station number 8518962 on the Hudson River in New York State, which gives most of the needed information (some conversions necessary), the WBGT Calculator returned the following:


29 C / 84 F — WBGT if in direct sunlight (assumes no clouds and a clear sky with an estimated solar irradiance of 487 W/m2).

23 C / 73 F —  WBGT if in shade (assumes a sheltered/shady outdoor location with solar irradiance = 0 W/m2).

*** NOTE *** If clouds were present, the WBGT likely was between the “direct sunlight” and “shade” estimates given above. This calculator does not attempt to adjust the WBGT for cloud cover. The reason is that such an adjustment depends on many factors–e.g., cloud thickness, cloud height, number of cloud layers, and whether or not the cloud was blocking the sun–that are difficult or impossible to determine in retrospect.

Are you beginning to see the difficulties in WBGT calculation – even for a single location and a single time?  Again, clouds, and their multi-layers uncertainties, get in the way.  Notice the range between WBGT (Sun) and WBGT (Shade), all else being the same.  And this is with a known wind speed, another wholly local element, which requires direct measurement and not estimation.

So, can anyone produce a wide-area map of the WBGT index for yesterday?  I don’t think so, not without a great deal more and more detailed information than is usually available from our even best weather stations. 

To measure heat stress conditions, a heat stress meter, which measures inputs and calculates WBGT, is needed.  U.S. Occupational Safety and Health Administration (OSHA) says this: “WBGT measurements are most reliable when taken at, or as close as possible to, the work area. When a worker moves between two or more areas with different environmental conditions, or when the conditions vary substantially in the work area, assess the heat hazard using representative measurements for the different conditions.”  For OSHA, this may mean measuring WBGT in each room or area of a worksite.  For school sports, “The WBGT [device] should be set up in the sun, not under shade. If you are practicing on turf, it should be set on the turf.” [ source ]  Not just anywhere at the school, not on the school quad or outside the principal’s office window, but actually on the playing field in the stadium where conditions will be different than in the spectator stands or on the sidelines. 

Bottom Lines:

1.  The WBGT index is a superior method of determining potential for heat stress for those working and exercising outdoors in the sun.

2.  WBGT depends on very local conditions.    These conditions must be accurately physically measured to be reliably used in any WBGT calculation.    The use of a purpose-built WBGT meter is recommended.  Much of this requirement is because “the formula is very sensitive to the value of the wind speed”  — wind speeds must be known to within 0.5-1 mph (0.8-1.6 km/hr) and are very sensitive to cloud cover, on which the value of solar irradiance hinges,  which can change minute-to- minute and hour-to-hour. 

3.  Claims to show wide-area WBGT index figures are suspect at best – WBGT is not a wide-area metric, but a local metric by its very nature.

4.  Obviously, if wide-area present-time WBGT calculations cannot be performed reliably, future wide-area prediction, such as that attempted by CarbonPlan, cannot be possibly made with any scientific degree of confidence.

# # # # #

Author’s Comment:

The Post/CarbonPlan “heat stress map of the future” is a fine example of what I have called computational hubris.   And results are shown in a “pretty pictures-manner – using a pretty picture to put forward a biased version of reality – usually in a way that does not explain anything. 

Again, in an effort push “dangerous heat”, the Post and CarbonPlan have misrepresented a heat stress index meant to be used very locally as something that can be calculated not only over spatially broad areas, which it cannot, but for the future.

I’d like to hear your opinions.

Thanks for reading.

# # # # #

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September 10, 2023 6:10 am

Personally, cold stress affects me more. In fact, recently I’ve delayed my morning bike ride for it being too cold outside.

Reply to  Scissor
September 10, 2023 8:41 am

Cold or even cool weather kills million more people each year than hot or warm weather worldwide. Breathing in cold or even cool air caused blood vessels to constrict causing increased heart and strokes in the cooler months.

Tom Halla
September 10, 2023 6:11 am

This looks very much like WAG claims pretending to be meaningful.

Reply to  Tom Halla
September 10, 2023 8:15 am


Wives and girlfriends….

Models, singers and graduates: Meet the WAGs of England’s Euro 2020 squad

Reply to  strativarius
September 10, 2023 9:04 am

Wild Ass Guess

Tom Halla
Reply to  strativarius
September 10, 2023 9:57 am

Tending in quality from a Wild Ass Guess to Pulled Out Of My Ass

Reply to  Tom Halla
September 10, 2023 2:04 pm

Where the likelihood of being right is equivalent to the chance that monkeys will fly out of my ass.

Joseph Zorzin
September 10, 2023 6:21 am

“The flooding had nothing to do with “climate change” – it was a fairly common stronger monsoon but with even more rain.”

Right. It happened in- get this- a FLOOD PLAIN- which has probably flooded a million times (or more) in the past few million years. I’m always amazed when people think a flood is an unnatural event. It’s only unnatural if our human created infratructure fails. (dams, poorly designed structures in the flood plain, deforestation in the watershed, etc.)

Reply to  Joseph Zorzin
September 10, 2023 7:14 am

“Oh no! It’s flooding in the flood plain!”

As you wisely point out, Mr. Zorzin, most of these events are all-natural occurrences.

People who sit around watching screens all the time, may not realize that the world’s most fertile farmland — where their food comes from — is flood plains with topsoil consisting of silt deposited by repeated floods over millions of years.

Scary stories on TV seldom include geology lessons.

Reply to  tom_gelsthorpe
September 10, 2023 8:11 am

Flood plains got flat from previous floods….

Reply to  tom_gelsthorpe
September 10, 2023 8:35 am

The don’t even mention that the earth is in a 2.5 million year ice age either when talking about hot weather. A 2021 study said 4.6 million die each year from cold weather compared to 500,000 from hot weather. Even the birds flee from the cold weather each year and fly south for the winter. Most of the earth is uninhabitable by human without technology in the form of warm clothes, warm houses, warm transportation, warm workspaces and the like.

The environmentalist, news media and politicians are supporting a very environmentally unfriendly policy. Letting the earth warm up will allow much more life to exists on the planet and many few human deaths from cold weather as well.

Reply to  scvblwxq
September 10, 2023 10:04 am

Birds towards warmer climate as the season changes due to food availability… But point taken… life generally abounds in the presence of more warmth.

Joseph Zorzin
Reply to  tom_gelsthorpe
September 10, 2023 9:10 am

Pakistan now has well over 200 million people living in that flood plain- then they wonder that there is a problem.

Joseph Zorzin
Reply to  Kip Hansen
September 10, 2023 11:43 am

Building on the flood plain should be fine with proper engineering. The river’s feeder streams can have lakes built on them that are only partially filled or have no water behind some of the dams- to control heavy rains. Structures in any communities and on farms should be extra strong to resist severe damage from any mild flooding. Alarm systems can be established in case there is a threat to any communities and ways should be available to get to higher ground. I’m no engineer- just speculating based on common sense. Such a system of dams on the feeder streams was proposed here in western and central Wokeachusetts back in the ’30s for all the feeder streams going into the very large Connecticut River. A few were built- but then the enviros started crying about them- that all that engineering work would endanger whatever, blah, blah, blah. One dam was installed a few miles from me in north central part of the state creating a very nice lake which is one of the best kakaking lakes in the entire region. A few hundred acres of forest was purchased by the US Dept. of Interior. They cleared the land for the lake and built the dam. Though it’s not a large lake it has numerous very small islands and it has a very irregular shore line so it seems much larger. Yes, of course Pakistan is a poor country- but they spend a lot on the military. If they had spent a fair amount every year since its civil war with India- it could by now have a highly engineered landscape. I doubt there are many enviros in that conservative Moslem nation. They just didn’t do it. Or maybe they did do some- I don’t know. Given how severe the damage was in recent flooding I presume they didn’t give the issue much attention.

Reply to  Kip Hansen
September 10, 2023 6:22 pm

According to my (very limited) reading, the political power in that country is controlled by an population that differs substantially (in their minds, at least) from more recent emigrants Those in power are of the majority population group that existed when Pakistan was created in the late 1940s. A large portion of later emigrants could logically be labeled refugees.

That political power group forced a large portion of the refugees to locate in that flood prone part of the country, where few other citizens cared to live: de facto segregation. Not a lot of public funds are expended on unwanted people, although they are undoubtedly a useful token in foreign aid requests.

Gilbert K. Arnold
Reply to  Kip Hansen
September 10, 2023 9:38 pm

Yes fllod plains can be managed… after the 1972 flood in Rapid City, SD, the city cleaned up the mess and then determined (as close as possible) the limits of the 100 year flood plain.and mandated that no permanent dwellings would be allowed in that zone. Now, following the course of Rapid Creek through the city are parks, picnic grounds ball fields,a bike path golf courses.. So it can be done provided the political will and funding is there

Reply to  Gilbert K. Arnold
September 11, 2023 5:06 am

And then along comes another higher flood than the last 100 year flood… reset the limits and try, try, try even again.

Of course the same limits do not app;y to the coasts where people aggregate. Insurance and natural risks do not apply.

Common sense where are you?

Gilbert K. Arnold
Reply to  corev
September 11, 2023 10:57 am

I did an analysis of that flood for my engineering geology class. The 1972 flood was something like a once -in-750 yr flood.a 100 year flood simply means there is a 1% chance of a flood of that size occurring each and every year.(and that does not preclude there being more than one such event in a year) A 100 year flood is an indicator of volume of water flowing past a point, a time interval.

Gilbert K. Arnold
Reply to  Gilbert K. Arnold
September 11, 2023 10:58 am

…not a time interval

September 10, 2023 6:24 am

Anything that “uses new models” is no more believeable than anything that used old models. Our understanding outside the hallowed halls of computers hasn’t budged a smegging inch.

When you focus on shooting everything else you don’t like down you aren’t learning a thing.

Ron Long
September 10, 2023 6:25 am

Kip, thanks for the review of The Wet Bulb Strategy, derived by the Dim Bulb crowd. Personally, I only recognize two WBGT environments, that is, I either walk on the sunny side of the street, or on the shadow side of the street.

Steve Case
September 10, 2023 6:28 am

Because a large segment of the population isn’t buying the “Climate Change” narrative. left-wing media outlets need to come up with a new way of predicting disaster hoping that it will successfully recruit new believers. Who knows, maybe a few people will change their minds, but maybe some of the believers will jump ship.

general custer
Reply to  Steve Case
September 10, 2023 7:39 am

Left-wing media outlets are merely passing along the information that they get from research academia. Nobody, including the media, takes seriously or is even aware of, the controversies in university programs in drama, literature, social work, psychology, art history, gender studies, etc. Why should climate “science” have more credibility?

Jeff Alberts
Reply to  general custer
September 11, 2023 7:38 am

I disagree. I think they’re fully aware.

Reply to  Steve Case
September 11, 2023 5:14 am


general custer
September 10, 2023 6:30 am

The WBGT is an example of the increasing occurrence of scientism, in this case the use of numbers in specious observations to reach a pre-determined conclusion. The most important statement in the above is that WBGT is “ Just a number that can be compared only to other numbers of the same index. It is not a measure of sensible heat.” It’s not a reality but an abstraction.

Reply to  Kip Hansen
September 10, 2023 4:00 pm

When I was young, local soccer down under was played in the winter months.

Evening practice was called off once the field was a quagmire.. or ice started to form. !

If you complained about the cold.. coach just said.. “you need a couple more laps round the field then”.

WBGT not required.

Tom Abbott
Reply to  general custer
September 11, 2023 10:47 am

Working or playing outside in high humidity and high temperatures is much more draining, than working in low humidity and high temperatures.

Anyone who works or plays outside in the summer needs to be aware of the heat index.

Rich Davis
Reply to  general custer
September 11, 2023 1:28 pm

Yes, it’s an index and thus an abstraction but so is a temperature scale such as degrees Celsius or Fahrenheit. Those are based on the thermal expansion of mercury or alcohol. It is still useful and in the sense that it gives a meaningful number that is reproducible under similar conditions, it is “real”.

WBGT is another more complicated abstraction that gives a better idea of whether a human’s transpirational cooling system (sweat) will operate effectively in an environment. The black copper globe is an empirical measure of effective solar insolation. Wet bulb temperature is an empirical measure of relative humidity. Wind speed determines how much the boundary layer of air is disrupted to carry away heat and evaporate sweat.

Anyone who has been in Arizona just after sunset when the air temperature is still 40°C will know that this works. What would be unbearable in a wet environment like Louisiana is comfortable in the very dry desert.

The point to be taken in Kip’s criticism is not that WBGT is an invalid abstraction. It is that it can’t be arrived at reliably through shortcut computer models. A bit more cloud cover or haze can make a big difference on the globe temperature at the same relative humidity and wind speed.

michael hart
September 10, 2023 6:49 am

Ahh, good times. Back in the 1980’s the environmental science department at the University of Lancaster, (Lancashire) would send scienceundergr aduates into the carpark to swing a wet bulb in the driving wintry rain.

Well, you’ll be forgiven for not being surprised that it registered the same as the dry bulb. 100% humidity at 5 Celsius. Not nice, but it’s grim up North as they say over here.

michael hart
Reply to  Kip Hansen
September 10, 2023 1:15 pm

The story I still like to tell is about the Nigerian student.
He arrived early for the academic year, in August. A very good August, as I recall.

He asked me when the rainy season ended. I almost felt like crying for him.

Reply to  Kip Hansen
September 10, 2023 6:26 pm

landscape changes can modify climate zones

Rich Davis
Reply to  Kip Hansen
September 11, 2023 1:35 pm

Better repeat the measurement until you get it right! Are you sure you’re swinging it fast enough?

September 10, 2023 6:55 am

The New! Improved! WBGT Index uses a metal globe painted black and positioned in direct sun to simulate the perceived heat of a person working outside. As such, it sounds like the pseudo-scientific equivalent of the “cooler” — a metal box where the prison camp commandant locked the British captive in the war movie “Bridge Over the River Kwai.”

In other words, WBGT is a torture chamber used to intimidate the other prisoners. If there’s any science in this, it’s the science of propaganda to induce fear and despair into unwitting civilians held captive by climatista activists.

Steve Case
Reply to  tom_gelsthorpe
September 10, 2023 7:17 am

Colonel Nicholson came to his senses in that 1957 opus. It’s up for grabs if today’s mad hatters club will ever do the same.

Tom in Florida
Reply to  tom_gelsthorpe
September 10, 2023 8:57 am

“uses a metal globe painted black and positioned in direct sun to simulate the perceived heat of a person working outside”

Yes, a silly methodology. I wonder what the “person working outside” would be wearing? Or is that based on the person being naked? Is it a lilly white Norwegian or a satin black African? Is the person a fat, blubbery slob or is the person healthy and physically fit? Is the person a male, female, both or neither? And so on and so forth…..

Tom in Florida
Reply to  Kip Hansen
September 10, 2023 6:47 pm

Kip, using qualifying conditions of the person, clothing, physical conditioning, type and duration of work or exercise is the proper way to evaluate the heat stress upon an individual. What I find silly is using a finite number to insist that is the danger point for everyone without any qualifying conditions.

Reply to  tom_gelsthorpe
September 10, 2023 6:41 pm


metal globe painted black and positioned in direct sun

(with a thermometer in the center) is a real thing and it isn’t a big stretch to suspect that the thermometer reading, compared to a more conventionally placed thermometer, might actually be some measure of the visible and infrared radiation (usually sunlight) striking the globe.

That is to say, might produce readings that relate to the conventionally placed thermometer in some consistent way. That would need to be confirmed by some independent measure, of course. If true, there is probably a way to make some legitimate use of it. Since radiation striking the human body does have experiential and measurable results, the measure of globe might be applied to reliable predictions of the effect upon the body.

The point of this article is that the measure is being used in an inappropriate and unreliable way.

Rich Davis
Reply to  tom_gelsthorpe
September 11, 2023 1:52 pm

Nonsense. Nothing wrong with the metric which accurately warns you if conditions are dangerous, provided that it’s measured using the actual meter.

Kip’s concern is when the CAGW loons want to shortcut the measurement by correlating the globe temperature to the longitude-latitude, time of day, day of year, air temperature, wind speed, and relative humidity, and interpolating measurements at nearby weather stations for wind speed and relative humidity which could be significantly different due to local terrain.

A model can of course be used to estimate the globe temperature (the black copper globe that measures solar gain, not the earth), but how to account for clouds, haze, windbreaks, a local stream, transpiration from plants, solar gain on a large adjacent asphalt parking area?

Tim Gorman
September 10, 2023 7:12 am

OMG! This is nothing more than the old familiar “heat index” we’ve had forever – with a few extra variables thrown in!

This has *NOTHING* to do with predicting the future “heat index”. It’s nothing more than more of the old IBM “FUD” factor (Fear, Uncertainty, Doubt) being used by climate scientists trying to rationalize their belief in CAGW in order to keep the money and power flowing!

My Vantage Vue weather station calculates what it labels THW. It’s the heat index (temp, humidity, wind). I’ve had it since 2012. If I were to add a UV meter it would calculate THSW (temp, humidty, sun, wind).

And these folks think they have come up with something new?

Reply to  Tim Gorman
September 10, 2023 7:58 am

It seems like they explain the need for shelter and air conditioning with their advanced science.

Tim Gorman
Reply to  Kip Hansen
September 10, 2023 12:12 pm

This is truly the old “one size fits all” prescription. The tolerance for heat stress is individual. Making those who can tolerate the heat sit out of learning or working situations because someone else is not as tolerant is just driving everyone to the bottom.

If 44 out of 45 football players can tolerate the heat should they all miss out on practice time because the 45th person cannot?

Reply to  Tim Gorman
September 10, 2023 6:47 pm

Equal outcomes for everyone means the lowest common denominator. Can’t hurt tender feelings by making someone feel they are less in some way.

Jeff Alberts
Reply to  Kip Hansen
September 11, 2023 8:38 am

The orginal WBGT was cookedup by the US Military in the 1950s”

Yes. I was in basic at Ft Knox in 1981, June through August. They used Wet Bulb indicators to determine what type of training could occur on any given day, if it was within a certain range.

September 10, 2023 7:24 am

 A WBGT over 89.6°F is the level at which there should be no strenuous outside work or exercise in the direct Sun

And presumably 89.5°F is no problemo — yeah right.

Tim Gorman
Reply to  karlomonte
September 10, 2023 7:36 am

OMG! I can’t tell you how many hay bales would have been left in the fields to collect moisture when I was working in the hay fields back in the 60’s and early 70’s if we went by this recommendation!

What a bunch of whiners we have today! I actually picked up loose hay using a pitchfork when the baler quit in 100F temps. And my grandparents on the plains did this routinely in harvesting grain as well as hay! Wearing blue cotton work shirts and overalls no less!

I don’t remember *anyone* dying when I was working the hay fields. Stopping to rest and sitting under the hay wagon in the shade for a while but not working? Pete forbid!

Reply to  Tim Gorman
September 10, 2023 7:52 am

Where did 89.6°F come from? Converting 32.00°C to °F! If they knew anything, the limit would be 90°F, but it is clear the 32°C is an arbitrary ad hoc number.

Reply to  Tim Gorman
September 10, 2023 8:34 am

Above “100 in the shade” was when we took the afternoon off baling…it meant starting at sunup the next day…

Reply to  DMacKenzie
September 10, 2023 1:13 pm

We couldn’t start at sunup. We had to wait for the dew to dry off. Otherwise we risk burning the barn down.

old cocky
Reply to  Kip Hansen
September 10, 2023 11:21 pm

those that have actually “humped hay bales” (picked bales up by hand and hurled them onto a moving hay wagon) have the full reality of haymaking.

You must do it differently over there. We used a bale elevator attached to the truck, largely because we loaded 6 or 7 bales high. That’s hard enough work, with 80 lb. bales. Stacking in the shed was the hard work, especially the last couple of half rows at the front of the shed.

The hay must be dry before baling or it will 1) Be ruined and 2) Can generate so much heat that it spontaneously combusts in the hay loft — which is very very bad.

Wet hay can get mouldy. Green hay can spontaneously combust.
The test for the cereal straw being dry enough to press was to pick up a handful from the windrow. Holding it with one hand at either end with 4 inches between hands, twist it like turning a crank. If it doesn’t break within 3 twists, it’s still too green.

There are good reasons for all the steps in haymaking, but people who have never made hay regard them as arcane or tradition until they are explained.
</nostalgic digression>

Tim Gorman
Reply to  old cocky
September 11, 2023 5:49 am

The use of a truck and elevator was only for the “rich” hay crews – those crews that could be afforded by “rich” farmers. When I grew up there were only one or two of those in the whole county. I considered myself lucky if I could load directly off the baler onto a wagon hitched to the baler while riding on the wagon. Otherwise it was hump four or five bales off the ground onto a wagon behind a tractor, jump on the wagon, stack the bales quickly, and then get back on the ground to pick up the next set of bales.

It wasn’t just the weight of the bales that was a problem stacking hay in the barn – it was walking on the previous layer and dragging bales across it. It was like walking and dragging in fine sand – a real workout for the legs as well as the arms and torso!

Doing loose hay with a pitchfork was still the hardest work I ever did – and *dirty*. Gave me a real appreciation for how hard prior generations had to work to survive.

Tim Gorman
Reply to  Kip Hansen
September 11, 2023 4:28 pm

I’ve never raised goats but the neighbor has. I can’t say they will eat anything but it’s close. They *will* eat the paper off of tin cans, which is the source of the myth they can eat the can.

I don’t think pitching it dowhill helps much. I had to have the old farmer I was working for show me the tricks like twisting the pitchfork to hold the hay and how to insert it into the pile so it didn’t just slide off. It didn’t take long for the blisters to form, even with good leather gloves.

old cocky
Reply to  Kip Hansen
September 11, 2023 8:44 pm

Kip. the stacking pattern is quite important. It has to be stacked so the layers key into each other, somewhat like laying bricks.
Good, uniform bales play a major factor as well.

Tim Gorman
Reply to  Kip Hansen
September 12, 2023 3:22 am

I never had an avalanche but I can see how it could happen, especially with the old-style round bales ( the little ones, not the big ones). As those balers wore out the middle of the bale wouldn’t get much for hay allowing the bale to collapse when stacking other bales on top of it. I worked some for a farmer that had an old wore-out baler and we couldn’t actually stack his hay for fear of it pushing the sides of the barn out and collapsing everything. We threw the bales through a window about 5 feet higher than the wagon and just let them “tumble” stack as they would.

old cocky
Reply to  Tim Gorman
September 11, 2023 8:32 pm

Maybe we were rich, Tim, but we seemed to be fairly typical for the district.
When the government was doing land sales in the 1870s (or thereabouts), the basic block size was 2,560 acres (4 square miles). That was enough to run 1,000 sheep or 100 head of cattle, and was intended to be enough to support a family.
The 4 square miles was more often 4 miles by 1 than 2 by 2, so it could be a fair distance from the wheat or oats paddock to the hay shed.

walking on the previous layer and dragging bales across it. It was like walking and dragging in fine sand 

Wire-tied bales of cereal hay from the old Sunshine pickup balers were around 70 or 80 pounds, and very firm, so it was quite easy to drag the bales across the floor. The best we could safely get from the New Holland PTO baler was about 50, which was spongy by comparison.

I can’t say I miss harvesting oats or feeding out oaten hay or oats in droughts when it was 110 in the shade – and there was no shade on the feed grounds.

Tim Gorman
Reply to  old cocky
September 12, 2023 6:45 am

Your hay must have bee “smoother” than the brom and prairie hay we put up in the barn.

old cocky
Reply to  Tim Gorman
September 12, 2023 3:00 pm

Cereal hay is certainly much smoother than lucerne (alfalfa) hay.

We only grew hay and oats for drought feeding, and hoped we wouldn’t have to feed it out for at least another decade.

Tim Gorman
Reply to  old cocky
September 13, 2023 5:46 am

That’s different than here. Hay is pretty much a winter feed except in the large cow lots feeding cattle up for slaughter.

September 10, 2023 7:36 am

wind speeds must be known to within 0.5-1 mph (0.8-1.6 km/hr)

Note that commercial wind cup anemometers have a low-wind-speed dead zone and cannot measure speeds less than 0.5 m/s (1.1 mph). Measuring low wind speeds usually needs a much more expensive ultrasonic anemometer.

Curious George
September 10, 2023 7:59 am

When does an average temperature kill?

Tom in Florida
Reply to  Curious George
September 10, 2023 8:58 am

Soon, very soon.

September 10, 2023 8:35 am

The AGW enthusiasts keep trying to come up with some empirical evidence, or at least what they would call empirical evidence, to prove their ‘theory’ (sic). As usual, they not only fail but beclown themselves in the process.

Reply to  mleskovarsocalrrcom
September 10, 2023 2:06 pm

In the meantime, they have to replace their old models with new models so that when the old models inevitably fail they can say that was only an old model use the new one. Just as perpetual motion machines need ongoing injections of energy, it’s a system that needs ongoing injections of money.

September 10, 2023 8:36 am

My spouse and I frequently check AccuWeather on DIRECTV. As a long-time weather watcher who has lived and worked from coast-to-coast, border-to-border, in Alaska (summer only), and the Philippines, it irritates me when they discuss their “extreme” hot temperature forecasts. They seem to purposely conflate actual measured temperatures with their higher “RealFeel” temperatures, or at least they don’t make it clear which values are being displayed. Summer conditions around the country that used to be considered “normal” are now portrayed as life-threatening. Temperatures that used to be colored green on TV around the world are
now in the brightest reds they can find. Next they’ll probably be flashing reds with sirens. As a really old guy I’m more than a little irritated that scientists, meteorologists, politicians, the MSM, Hollywood, and “educators,” are all in on the “Chicken Licken, the sky is falling” hoax/BS.

Mr Ed
September 10, 2023 8:57 am

WetBulb ha that’s a good one, I remember the skipper declaring “tropical work hours” back in the day in SE Asia and later in the IO, and the memories of my first monsoon experience. It came in like a black wall getting darker and darker and the first drops hitting the ground the size of silver dollars. The water was running down Main Street in Olongapo waist deep a day later. I saw the same thing in E Africa years later. In a different life I recall pouring myself out of my boots at the end of a day making hay or some such after working in the fields..

September 10, 2023 8:58 am

Kip, This is a very good article.

Kevin Kilty
September 10, 2023 9:03 am

An outfit with the name of CarbonPlan is pretty obviously an activist group with particular agendas to push. Putting activists in charge of something, anything that is supposed to be an objective index is asking for … well, activism. Expect truth to be a casualty.

Kevin Kilty
September 10, 2023 9:20 am

It is interesting to note that the hotter and more humid parts of the country, Region/Category 3 (dark grey) have higher allowable WBGT index readings and the cooler, less humid regions have lower allowable index readings.

Yes, interesting. I went to the reference and this is entirely arising from the sensible observation that people become acclimatized. I have doubts about the usefulness of the map, especially its coarseness, however.

Tim Gorman
Reply to  Kip Hansen
September 10, 2023 12:17 pm

That still means the supervisors, coaches, employers, work safety types have to make an individual judgement as to when the cutoff is reached.

What will happen is that the school district, OSHA coordinator, etc will set the same guideline for EVERYONE, even if one school is up in the mountains and another down on the river plain.

I know and you do to that this is *exactly* what will happen. Everyone will get driven to the bottom where everyone is “equal”.

Reply to  Kip Hansen
September 11, 2023 2:26 am

intended to be a guide”

Like the book “1984” ?? 😉

September 10, 2023 9:23 am

This is yet another example of creating studies that sound and look all technological and sciencey . Worse yet working outside in hot humid weather can be miserable( who knew! ha ha) So now every time it is hot and humid gullible sheep people will be thinking “ oh my god is this going to be our future everyday”

I am loosing hope for us . It is like half our population needs a slap in the face like in those old movies: “ Come on man get grip, snap out of- SLAP! … thanks I needed that.”

John Hultquist
September 10, 2023 9:29 am

 (I took time off from this research project to help my son paint a local widow’s concrete front porch on a 90°F day, in the hot direct sun.)  

I helped with a similar chore at age about 17. It required a lot of cold beer.

{Did you know that the length of Arlo’s song is the same length as the 18.5- minute gap in the Nixon WH tapes?}

September 10, 2023 9:59 am

Nice! Again, It comes down to clouds. They don’t understand and/or cannot account for them. Sounds familiar?

September 10, 2023 11:47 am

Great. Another temp-measuring scheme to construct and manipulate.

Tim Gorman
Reply to  beng135
September 10, 2023 12:18 pm

You can bet your bottom dollar that sooner or later 70F will become the standard. No one practices football outside if the temp goes over 70F. The personal litigation lawyers will insure it!

Reply to  Kip Hansen
September 11, 2023 5:52 am

I wonder how/if those thresholds have changed since the widespread imposition of covid vaccinations? Every week there’s an article about someone dropping from a heat attack during sports.

Alexy Scherbakoff
Reply to  beng135
September 10, 2023 2:30 pm

It will become the ‘Woke Bulb Global Temperature’ before too long

September 10, 2023 1:56 pm

When actual temperatures aren’t scary enough these knuckle draggers need to come up with made up systems to scare the living crap out of gullible people. They are disgusting.

Edward Katz
September 10, 2023 2:20 pm

If heat poses such a danger, why is it that the countries with some of the hottest climates also have the world’s highest populations? India has the 2nd most people or maybe it’s taken over top spot now. Indonesia is 4th and it’s followed by Pakistan, Brazil and Nigeria, the last of which has one of the fastest growing populations on earth. Shouldn’t the heat that these countries experience annually and regularly be reducing their populations? And shouldn’t northern Canada, Alaska, Scandinavia and Siberia growing much faster since they don’t have to face any major threats from the alleged global warming effect?

Reply to  Kip Hansen
September 10, 2023 7:00 pm

Increasing prosperity and education levels slows population growth and it eventually levels off and starts to drop.

Isn’t that evidence that education and prosperity are life threatening? Perhaps our masters really do have our best interests at heart.

Reply to  Kip Hansen
September 11, 2023 5:56 am

The most plausible reason that those hot countries have exploding populations is that there’s less clothes in the way of “getting things done”… eh?

Gunga Din
September 10, 2023 2:34 pm

I suppose that if they were promoting “Global Cooling” then those died in a hurricane or tornado would be listed as victims of “Wind Chill”?

Clyde Spencer
September 10, 2023 3:10 pm

The analysis is based on a measure called wet-bulb globe temperature (WBGT), …, and is increasingly used by scientists to determine how heat stresses the human body.

Yes, it does seem to me I’m seeing WBTs being reported more frequently, albeit with them not always explicitly identified as such. Thus, people might get the impression that the former simple temperatures have increased significantly lately. More game playing?

September 10, 2023 3:32 pm

“A WBGT over 89.6°F is the level at which there should be no strenuous outside work or exercise in the direct Sun…”

That’s one of the reasons that I live in Category 1. But being in direct sunlight here even on a 70⁰ day can quickly become uncomfortable. Conversely, even during the warmest days, the shade is comfortable in summer. Given other factors, personal preference and metabolism being perhaps the biggest ones, I’ve always wondered how they determine the “feels like temperature” (heat index and wind chill). It’s all subjective.

September 10, 2023 5:49 pm

In 1979, the US Air Force School of Aerospace Medicine published this paper establishing the “Fighter Index of Thermal Stress”–an index the USAF has been using for over 40 years, now.


September 11, 2023 5:08 am

To the average Joe, the WBGT is too confusing to understand the intimate details this blog post describes which is exactly what the WAPO wants. A clueless reader is their audience and $$$. The WAPO, NYT, CNN, MSNBC etc will be spreading and hyping the WBGT as the latest tool to anchor their global warming/climate change debate. If their audience cannot understand the details then they won’t be able to see the devil.

Bob Rogers
September 11, 2023 6:49 am

I walk the dog in the morning. It’s frequently hot and humid. As the sun rises, I notice a huge difference in comfort between being in the sun and being in the shade. To the extent that in the shade it’s actually pleasantly cool, while in the sun it’s unpleasantly hot.

It seems like WBGT is only potentially useful if you’re out working in a large field. Like say an Army unit on maneuvers in Fort Hood. Or maybe highway workers. In most places where most people live, at least here in the USA, you have a mix of sun and shade. If you’re working on the east side of a street in the morning you’re probably shaded by the buildings on that block. At my house, about half the yard is shaded at any point in the day, but at my friend’s house there is no shade, except when you’re on the correct side of the house.

This weekend we went to the neighbor’s house for an end of summer party. There was a breeze blowing through the area where the picnic table was. He said that the breeze always blows there. At our house, literally across the street, there’s never a breeze — like we had wind chimes up for a couple years and they only made noise during storms.

Seems to me like whoever wrote the article probably needs to spend more time outdoors.

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