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Glorious Northwest Summer Continues With High Temps and Mostly Clear Skies

Elaine Thompson
AP Photo
Jayden Matua, left, and T.J. Manulauti bask in waters of the International Fountain as they play in warm and sunny weather, Friday, July 13, 2018, in Seattle. Daily temperatures are expected to go back to around 90 degrees this weekend through Monday.

It’s been hot in the Pacific Northwest, with nearly two weeks of clear blue skies and temperatures near 90 degrees. There has been no rain in sight, just a glorious backdrop for mountain and water views, perfect weather for swimming or running through sprinklers.

Expect more of that over the weekend and through Monday at least, says KNKX weather expert Cliff Mass, a professor of atmospheric sciences at the University of Washington.

Slight Cool Down Friday

Friday started off a bit cooler, with marine air pushing in at lower levels of the atmosphere, bringing stratus clouds that had been on the coast to parts of South Seattle.

“So instead of being 90 or maybe 91, we’ll probably be 86-87 in parts of Seattle away from the water,” said Mass of Friday morning’s weather. “A definite slight cool down.”  

Clear And Warmer Saturday, Hot Again Sunday

But he says another warm-up is right around the corner. On Saturday, high pressure will start building and the influence of the cool marine air will remain strong enough to keep the air in the mid- or upper 80s, Mass says.

But then on Sunday, a ridge of high pressure will extend from the south over the region.

“I think we’ll be back to 90, low 90s in the region, so definitely a warm up on Sunday,” Mass said.

Back To Normal By Wednesday

The higher-than-normal temps for this time of year will start to subside as the workweek begins, Mass says.

“We’ll stay warm – maybe slightly cooler on Monday and Tuesday," he said.

"But then there's a big change: An upper-level trough (of lower pressure) – a major one – slides in off of the North Pacific. And temperatures will come back to normal range.”

Lower pressure makes the temperatures drop. That spells the end of our recent heat wave.

So, if hot weather is your thing,  do what you can to enjoy it this weekend. Because it won't last much longer.

“No more upper 80s. We’ll be back into the upper 70s. And I think we’ll have several days of near normal temperatures starting around Wednesday,” Mass said. “The end is near.”

To hear the full conversation, including Cliff’s discussion of why most Pacific Northwesterners can enjoy the heat without air conditioning (hint: think relative humidity and dewpoints, ) you can click on the 'play' icon at the top of this post.

Weather with Cliff Mass airs at 9:02 a.m. Friday, right after BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KNKX environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington professor of atmospheric sciences, a renowned Seattle weather prognosticator, anda popular weather blogger. You can also subscribe to podcasts of Weather with Cliff Mass shows, viaiTunes or Google Play.

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