Why Seattle’s summer has been off to a gloomy start

It’s generally accepted that summer weather doesn’t officially start in the Seattle area until after the Fourth of July. What we’ve seen this year, though, has been a continuation of what was a gloomy June.

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According to University of Washington climate scientist Cliff Mass, Sea-Tac (where Seattle’s weather is measured and tracked) hasn’t seen a single day in July so far where temperatures have reached normal values for that period.

“Sunshine? Much less than normal!” Mass noted.

Seattle Weather Blog’s Justin Shaw also points out that this is the coldest start to July that Seattle has seen in 15 years. Through the first eight days of the month, the city’s average temperature was 62.5 degrees, a full two degrees below what’s normal for that period.

This could possibly beget a cooler summer when it’s all said and done. Shaw cites data from the five years where July started with weather that has been cooler than what we’ve seen in 2020. Of those five years (1993, 1999, 2000, 2002, 2005), a 90-degree day wasn’t seen in three of them. In the two that did see 90-degree weather, 1992 saw just one such day, while 2002 saw two.

Cooler weather seems likely to continue, according to the 6-10 day forecast from the National Weather Service, predicting colder temperatures for the entire Pacific Northwest over that time.

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Mass attributes this to “a pattern with higher than normal pressure offshore, but lower than normal pressure over the Northwest.” That’s what brings in the “cool, cloudy marine air” Western Washington has seen in recent weeks.

Likening Seattle’s summer weather to the 2014 crime thriller Cold in July, Mass doesn’t see that trend stopping anytime soon.

“This does not sound like it is a flick with a happy ending,” he opined.

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