Are Weekends Wetter than Weekdays?

Reposted from the Cliff Mass Weather Blog

I have been hearing from a lot of folks suggesting that our weekends have been wetter than our weekdays, and asking me whether this was true.

So is it true?  Are the weather gods preferentially punishing Puget Sound residents over the weekend?

Are the weather gods punishing us?
Let’s find out! 

To do this, I secured the daily precipitation statistics at Seattle-Tacoma Airport for May and June so far–43 days in all.

For the full period, there was 4.04 inches at Sea-Tac for .09 inches per day.

For the 31 weekdays, there was 1.72 inches in the rain gauge, or .05 inches per day

But for the 12 weekend days, there was 2.32 inches or .19 inches per day.

Yikes! It is true!  The weekends have been wetter, with nearly FOUR TIMES MORE PRECIPITATION PER DAY THAN DURING THE WEEKDAYS.
Good reason to complain.  But is this a real effect or just chance?

There have been a number of investigations of this serious topic, a recent one led by one of my ex-students:  Professor David Schultz of the University of Manchester.  Their conclusions based on examining the data from 219 stations across the U.S for the period 1951-1992 was:

“neither the occurrence nor amount of precipitation significantly depends on the day of the week”

A conclusion illustrated by this figure from their paper:

Other earlier papers have produced contradictory results.  Some have suggested that weekly variations in pollutants from industrial processes, aviation, and driving would influence precipitation processes, thus producing a weak weekly precipitation cycle.  But lets face it, such effects would be greatly minimized in this period of COVID-19 shutdowns and the protest-related fires did not start until late in May.  A plot of the concentration of particulates over Seattle does not suggest a weekly signal at all, with relatively clean air over Puget Sound for the period (see below, 5-10 is clean air).

I suspect strongly that this precipitation pattern is just bad luck, an unfortunately roll of the meteorological dice and will not continue into the summer.  Yes, it is raining today.  But according to the excellent weather.com forecast, tomorrow (Sunday) should be mainly dry, showers will be around Monday and Tuesday, and next weekend should be dry.

But providing an offering to your favorite weather god might not be such a bad idea, something meteorologists like myself are well practiced at.

In my department, we instruct the uninitiated how to appease the weather gods

55 thoughts on “Are Weekends Wetter than Weekdays?

  1. Just random variability…but it would be great someday if we could order the rain to start Sunday evening at 10 Pm, and clearing by 8 Am Monday morning for a week of sunny skies, with every week guaranteed at least a half inch rain every Sunday evening. This is the equivalent rationale of thinking we are going to limit the climate system to 1.5-2 degrees of warming by 2100 if we just spend $3 Trillion on “climate initiatives” by 2030, just for a start. Are people really this stupid? Maybe we are 1.5-2 degrees colder by 2100, just due to natural variation like the LIA was.

        • It use to be that the “air polluters” situated to the West of someone usually got blamed for their “rainy” weekends.

          The Monday thru Thursday generated “smog” (industrial pollution) in Indiana and Ohio would surely be the cause of the weekend rain in eastern New York and New England.

    • Basic reason should lead one to realize that weather sprites, having never developed the calendar nor writing, have no way of knowing which day of the week it is and therefore cannot coordinate their patterns.

  2. I traveled a lot in 1983-1984 — 208 days away from home out of 366. What I noticed in the winter and spring of 1984 was that Thursdays were simply deadly days to travel in/out of ol’ Stapleton Airport in Denver. I had flights cancelled, got rerouted, Continental airlines planes side-e-ways on the one functioning runway, etc. Fourteen straight Thursdays of inconveniences to travel. Weather seems to present patterns that persist for a while and then reset.

  3. A weather prediction-time honored is:”Partly to mostly with a chance of.” then you have either-everyone satisfied -or not.

    • In summer 1969, I commuted each week for the weekend from Rochester, NY to Beach Have, NJ. It rained almost every weekend for 10 weeks. The best I could figure during that time was that, being before the Clean Air Act, it took five days to accumulate enough particulate matter in the atmosphere to trigger a full round of thunderstorms. Afternoon showers are common, but, back then, the heaviest were in the weekends with fewer to none on week days.

    • The “rain” in those songs was the US carpet bombing of Vietnam from B52 bombers in the stratosphere.

      • Have another look :

        I went down Virginia,
        Seekin’ shelter from the storm.
        Caught up in the fable,
        I watched the tower grow.
        Five year plans and new deals,
        Wrapped in golden chains.
        And I wonder, still I wonder
        Who’ll stop the rain.

        That’s the FDR New Deal and Gold Reserve system that Nixon dumped, causing the economic implosion right now, decades later as precisely forecast.
        Who’ll stop the rain right now?
        The Vietnam “runnin’ through the Jungle” is something else. Bannon et al seem to relish that stuff.

        • Which economic implosion was forecast? I have lived through several, none predicted reliably. We had plenty when the US was still on the gold standard. This statement , like the weather being worse on weekends is a good example of confirmation bias rather than a statistically significant pattern.

          • I have seen studies showing that Economists’ forecasts have a much worse batting average over their period of forecasts than Meteorologists. Which really frustrated me when I was a weather forecaster because they got paid a lot more money to do a poorer job. (unless it was a con job then they were doing a pretty good job)

          • Loren, you are correct.

            Richard Patton,

            I have seen studies showing monkeys throwing darts at the various Exchanges lists of stocks had a better batting average than the stock pickers.

          • Loren, you are correct.

            Richard Patton,

            I have seen studies showing monkeys throwing darts at the various Exchanges lists of stocks had a better batting average than the stock pickers.

  4. It is not good time to come to any conclusion, at least not until road and aviation traffic is back to normal.

    • Around here it is often said “it always rains on weekend”, which of course is not true, but I decided to have a look at data anyway. SE England with the greatest volumes of the road and air traffic (2018) is as good choice as any.
      http://www.vukcevic.co.uk/SE-UK%20rain.htm
      Sure no 7 day, but there is some kind of quasi-periodicity with a sharp peak at 22 days (?!)
      … may be something to it, but with low probability since 22 days just over 3 weeks.
      … or do you know any differently?

  5. In my department, we instruct the uninitiated how to appease the weather gods

    I presume it has something to do with buying the drinks for more senior department members?

  6. ‘Some have suggested that weekly variations in pollutants from industrial processes, aviation, and driving would influence precipitation processes.’

    Has pollution, particularly particulates from coal fired power plants, been factored into the climate models?

  7. They’re being punished for being woketarded. Just wait until the Cascadia Subduction Zone earthquake and tsunami hit.

  8. One thing is probably true that where a persons occupation involves being indoor 5 days a week and his weekends involve being outdoor , watching or playing sport , gardening, exercising, etc any rainfall at the weekend would be more noticeable even if not more prevalent.

  9. Shame on you Clifford. You are not wailing from the alarmist minaret. It should be blindingly obvious to you that wet weekends are a consequence of AGW as your own data prove. and what is more it. WILL get worse,

    Stories that in Camelot it rained only at night are Heartland propaganda for the (now debunked ) Medieval Warm Period as the Mann from the State Penn has conclusively demonstrated.

    Regretfully for Saint Greta the Cross, it rains every day.

    Maybe we should crowdfund an umbrella for the poor dear

  10. You remember the disappointment when your weekends were rained out and the plans you had worked on so hard came to naught. You go to work whether it is raining or not. Not much to remember during the week.

    And that is probably why people have a suspicion that weekends get more rain.

    • Exactly !
      That’s why we feel that “it always rains on a Bank Holiday” It probably rains no more often on a public holiday than on any other day in the week in which it falls. (Though having said that, nearly all UK public holidays fall around Christmas and Easter, and only one in Summer/Autumn so the chance of rain on any one will be higher than average)

  11. Meanwhile, here in NH and I suspect much of the northeast US, it has been very dry. So if the weather gods would kindly send some of that excess moisture our way, it would be much appreciated.

    • Bruce,
      Here in the Great NorthWet (a bit south and east of Seattle WA), I have 2.4 inches of water in the rain gauge for the last 7 days. My lawn has standing water on it, because the soils have been saturated since last December. The side ditches along the roads are running water, unusual for mid June. We continue to have daily high temps in the mid 50s F to low 60s F. If it doesn’t dry out and warm up next week, we’ll be hunting for a patch of ground dry enough to set up for the 4th of July cook out!

      This is variable weather, within typical ranges though. It is not ‘Climate Change’, as so many of the low science believers here insist is ‘happening’. It sure as hell isn’t man made Global Warming. I’m still running the furnace!

  12. It’s called Confirmation Bias. The same thing that causes ER nurses and staff to believe that a full moon causes more crazy activity. They’ll look outside and see a full moon, and say “See!”. But on those days when there isn’t a full moon, they just forget about it.

  13. There was a rainfall dataset published last year for 2007-2018 and updated into 2019 using a “bottom-up” approach (soil moisture from satellite data). https://soil-modeling.org/resources-links/data-portal/sm2rain-ascat-2007-2018-global-daily-satellite-rainfall-from-ascat-soil-moisture

    I could envision workday particulate emissions and urban heat island effect being different (or at least distributed differently) than weekends, which could affect local and regional scales.

    But over sufficiently-large timescales, it would seem there would not be significant differences otherwise.

  14. Not that this is proof, but, Living near a lake I bought a Ski Boat for the kids when the eldest started HS. For the next two years there were only two weekends throughout the summer that it did not rain. The kids kept track of them. I would often take Friday afternoon off so I could take the kids skiing. I then rented a dock so that we could get an earlier start and it seemed as if it did not rain again on weekends. It definitely rained less less frequently on weekends than the previous two years.

  15. Fifty five years ago, while living in Hartford, Conn., we had a summer where it rained every weekend for 7 weeks. I asked a weather man I knew about this. His explanation was that it was not unusual for the weather to get into a 7 day pattern, so that the same weather would occur on a given day of the week for weeks at a time. Since then, even living in central Texas, half a continent away from Hartford, I have noticed that we will often have several weeks in a row where the weather is same (usually remember rain) on the same day of the week.

  16. Shame on you Clifford. You are not wailing from the alarmist minaret. It should be blindingly obvious to you that wet weekends are a consequence of AGW as your own data prove. and what is more it. WILL get worse,

    Stories that in Camelot it rained only at night are Heartland propaganda for the (now debunked ) Medieval Warm Period as the Mann from the State Penn has conclusively demonstrated.

    Regretfully for Saint Greta the Cross, it rains every day.

    Maybe we should crowdfund an umbrella for the poor dear

  17. In the six months I spent working in Sydney in 1987-88, we had eight successive wet Saturdays. And that was before “global warming” was any more than a scheme in the minds of certain politicians and bureaucrats.

    • There was a joke in Sydney at that time. What do you call the day after two days of rain? Monday!!!

  18. My mother used to do the week’s washing on a Monday, and always thought that Mondays were more likely to have rain:-)

  19. What you need to do is make a model proving that there is more rain on weekends. Include in the model how CO2 creates this extreme weather. Get Michael Mann to rubber stamp this model. I am sure Gov Inslee will use this model as proof why WA state needs to spend billions on climate change

  20. That was very interesting Charles.
    Now consider this: H2O and CO2 bond inversely proportional to temperature to form H2CO3, a.k.a. carbonic acid which makes both much more massive than the N2 and O2 making up 99% of dry air. If the heat island effect of cities causes air and CO2 to rise and the weekday emission from human activities are the greatest, the CO2 emission must increase precipitation. Perhaps a better example of the link between CO2 and precipitation was the unprecedented 2019/20 bushfires in southeastern Australia that were followed on 20 January by unprecedented hailstorms in Canberra, Australia’s capital city, which had been shrouded in smoke for a month. For YouTube videos of the hailstorms, just search for January 2020 hail storms Australia.

  21. This has to be the most BS article I’ve read in a long time.
    Of course it only happens in Washington state
    Here in Virginia, we’re thinking of working weekends, and taking two days off during the week when it’s not raining. It’s been absolutely beautiful here on the weekends; rains like crazy during the week..

  22. Here in the Land of Oz, bottom left, if we can persuade cold fronts to roll through on Tuesdays and Wednesdays we get rain-free winter weekends.

    Now all we have to do is persuade those cold fronts…

  23. I would like to study whether or not Environment Canada over predicts sunny weather for the weekends. It seems they do but the forecasts change so frequently that it is not possible to say exactly which forecast is the one to count. Much like screening tree ring datasets, you could pick and choose your forecasts to get pretty much whatever result you wanted.

  24. Bit like here in the UK where it is thought that Bank Holidays are wetter than normal days, so people spend weeks looking forward to a three day weekend only to find it tips it down with rain.
    A few years ago after the Met Office had spent the early part of the year bleating on about how it was going to be the “hottest driest” summer ever we had a cold wet summer so the Met office changed it to it going to rain till well into September so the August Bank Holiday would be a washout.
    Come the end of the month and low the weekend was warm and sunny over the whole country.

    James Bull

  25. “So is it true? Are the weather gods preferentially punishing Puget Sound residents over the weekend?”

    If the weather gods are not punishing Seattle, they should be!

    • May the PSCZ (Puget Sound Convergence Zone) park over downtown Seattle and Capitol Hill district for the rest of the summer. There, Curse armed and launched.

      In case you don’t know, the wind flow around the Olympics can cause an unusual weather phenomenon by forcing winds to converge on the lee side of the mountains forming an approximately ten-mile wide area of enhanced clouds and rain called the Puget Sound Convergence Zone which stretches across the sound sometimes to the foothills of the Cascade Mountains. Occasionally it can be so pronounced that north and south of the PSCZ the skies can be partly cloudy and in the PSCZ the skies will be overcast with light rain and drizzle.

  26. In six years of school in Scotland I do recall that summer was an annual event and usually occured on a Thursday.
    Cheers
    Mike

  27. Decade or so ago a local weatherman in Portland, OR looked at the data for the Portland area. He concluded yes it does rain more on the weekends. Think he looked over a couple years worth of data but memory is fuzzy on exactly what he said.

    • The meteorologists in the Portland Oregon area (both in the University of Oregon and National Weather Service) have done studies that prove everyone’s hunch that it DOES rain (slightly) more during the Rose Festival (early June) than the weeks before or after. They attribute it to the fact that that is about when the mean position of the polar front (weak though it may be that time of the year) transitions across the city, finally moving north of the city to end in northern BC/Southern Alaska

      • Oh, and by the way, Summer usually doesn’t start in earnest around here until the 4th of July. Portland gets less rain in July than any other U.S. city outside of the Desert Southwest. (0.57″). Summers here are beautiful; lots of sunshine, little rain, average high 81℉. [we aren’t going to talk about the dreary winters]

  28. It’s true! It’s true! The crown has made it clear.
    The climate must be perfect all the year.

    A law was made a distant moon ago here:
    July and August cannot be too hot.
    And there’s a legal limit to the snow here
    In Camelot.
    The winter is forbidden till December
    And exits March the second on the dot.
    By order, summer lingers through September
    In Camelot.
    Camelot! Camelot!
    I know it sounds a bit bizarre,
    But in Camelot, Camelot
    That’s how conditions are.
    The rain may never fall till after sundown.
    By eight, the morning fog must disappear.
    In short, there’s simply not
    A more congenial spot
    For happily-ever-aftering than here
    In Camelot.

    Camelot! Camelot!
    I know it gives a person pause,
    But in Camelot, Camelot
    Those are the legal laws.
    The snow may never slush upon the hillside.
    By nine p.m. the moonlight must appear.
    In short, there’s simply not
    A more congenial spot
    For happily-ever-aftering than here
    In Camelot.

    • Nicely done Mark but you forgot to mention how this was all decreed so the crown could hoard the coal and oil and dispense it to the Royals and all their elitist friends.

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