Climate Impacts, Temperature Trend Analysis

Heatless in Seattle Summer 2023

Posted on by Ron Clutz

With all the media noise about “Global Boiling”, they must think we are all frogs in a pot on the stove (electric, no gas permitted).  And yet, what a difference a year makes in the US Northwest, as Cliff Mass reminds at his blog A Summer Without Extreme Heat in the Northwest.  Excerpts in italics with  added images.

With all the talk of heat waves in the media these days, it is fascinating to note that the Pacific Northwest has NOT had extreme heat this summer.  

No major heatwaves.   A lack of warm temperature records.

A really moderate, benign summer regarding high temperatures.  And the temperate weather is not over.

And more surprises…there is really little evidence over the past decades of increases in extreme July heat in our region.

Let me show you some data, to prove the above to you.

Just a reminder….the end of July is climatologically the warmest time of the year (see the climatology of SeaTac Airport, below).   By the end of August, solar radiation has declined so much that the temperatures inevitably decline.

 

A July Without Extreme Heat

Below you will find plots of the highest temperature in July over many decades for five local stations:  Olympia and Bellingham in western Washington, Wenatchee and Kennewick in eastern Washington, and Portland, Oregon.  I have plotted the July highs for the entire period of record and plotted a linear trend line for your reference.

Really interesting.   The high temperatures in July at these stations have been very average and FAR below record levels.  

Most of you have not needed AC this month.

Perhaps Shocking to Some
Now look at the trend of the extreme July temperatures above (brown lines) and you will notice something that is perhaps surprising:  there are no large increases in record July temperatures over many decades.
About a 1°F increase at Bellingham and Olympia, roughly .5 °F at Portland and Wenatchee, and a DECLINE of roughly 2 F at Kennewick over many decades.
The background global warming of mean temperatures is about 2F.  Our regional extremes are going up LESS than that.  
There is no local amplification of extreme temperatures as the planet slowly warms.
To bring home the message of the lack of extreme temperatures this July, below are the temperatures at Olympia and Wenatchee (blue bars showing observed highs and lows), with record daily highs shown by the red colors.
No daily high-temperature records were broken.  None. Nada. Zippo.

Finally, the moderate temperatures are not over.  

To illustrate, the latest 7-day forecast from the European Center ensemble (shown below) indicates cooler than normal conditions (blue colors) over and west of the Cascade crest (this is for the daily average temperature, NOT the high temperatures).
As noted in my previous blogs, the lack of extreme high temperatures is associated with a persistent atmospheric circulation pattern.  It also helps explain the lack of wildfires over the region.

 

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