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‘Curse of the wet weekends’ has had a strong hold on our region. What's behind it?

A cloudy Friday night in Seattle, February 21, 2020.
Tim Durkan
Tim Durkan Photography
A cloudy Friday night in Seattle, February 21, 2020.

If you feel like you’re being punished by the weather for staying indoors during the workweek, you’re not alone. Lots of people in Western Washington have noticed a pattern of fair and sunny weather that abruptly turns to rain as soon as the weekend arrives.

KNKX weather expert Cliff Mass says he’s expecting what he calls "the curse of the wet weekends" to continue this weekend. (It may feel especially damning to those hoping to mark the summer solstice on Saturday or Father’s Day on Sunday outdoors.)

Mass says he’s heard from a lot of listeners, asking if this is just their imagination or if there’s something behind it. So, he took a look at the statistics.

“I looked at the numbers. And from May 1 until mid-June, it’s been raining a lot more on the weekends,” Mass said.  "In fact, four times more per day on the weekend than on the weekdays. So, it’s a real effect."

And there is some science that might suggest human causes behind the pattern. The idea is that the increased particulate pollution we have in the air on weekdays because of more industry and traffic could actually influence rainfall patterns. So there have been numerous studies looking into this.

“In fact, all precipitation has, at its core, a piece of dirt, a particle of something, which the water condenses on,” Mass said. “And so if you have more particles in the atmosphere, potentially, that could affect how much rainfall you get.”   

But he says the influence can go either way: it could both cause or prevent rain. And Mass says the most recent studies he’s seen show no clear correlation. So, despite the clear data in our region for this six-week period, he thinks what we've been experiencing is just unlucky coincidence.

“I suspect that this is just the dice being rolled in an unpleasant way,” Mass said.

He says around here, the strong influence of the Pacific Ocean provides ample circulation that keeps our air quite clean. Plus, recently, traffic and industry have been a fraction of normal due to restrictions because of COVID-19.

And despite the continuation this weekend, he isn’t worried about the extended outlook.

“I suspect it won’t be continuing into summer,” he said.

You can listen above to hear the full discussion. 

The weekly KNKX feature "Weather with Cliff Mass" airs every Friday at 9 a.m. immediately following BirdNote, and repeats twice on Friday afternoons during All Things Considered. The feature is hosted by KNKX’s Environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington Professor of Atmospheric Sciences and a renowned Seattle weather prognosticator.  You can also subscribe to a podcast of “Weather with Cliff Mass” shows on AppleSpotify and Google

Bellamy Pailthorp covers the environment for KNKX with an emphasis on climate justice, human health and food sovereignty. She enjoys reporting about how we will power our future while maintaining healthy cultures and livable cities. Story tips can be sent to