100 degrees in Seattle this week? What you need to know

Seattle on a hot day

You can already hear the groans and moans reverberating throughout Puget Sound.

A sprawling ridge of high pressure that’s been baking the Southwest for most of the summer will bulge northward in the next few days, sending temperatures soaring toward 100 degrees in Seattle by Thursday. The blazing heat is expected to stick around through at least Friday, with temperatures making another run at the century mark before gradually dropping back to the 80s in time for next weekend.

Record highs are likely across all of Western Washington starting as soon as Tuesday—and there’s even an outside chance Seattle’s all-time hottest temperature mark goes down in the inferno. Below are answers to some frequently asked questions about the upcoming heat wave. Be sure to follow along on Twitter for continuous, rapid-fire updates as the sizzling gets underway.

How rare is 100 degrees in Seattle?

Seattle has only reached 100 degrees three times since weather records began in the 1890s:

  • 103 degrees on July 29, 2009
  • 100 degrees on July 20, 1994
  • 100 degrees on July 16, 1941

If Seattle hits triple digits on Thursday or Friday, it’ll be the third time in the past 23 years—after only reaching it once in the first 100 years of weather observations.

So, 100 degrees would be a first for August?

Yes. Seattle’s current hottest August temperature on record is 99 degrees, first set on Aug. 9, 1960 and later matched on Aug. 9, 1981.

What daily high temperature records are likely to fall?

The current marks for Aug. 2, 3 and 4 (Wednesday through Friday) are likely toast.

  • Aug. 2 record high: 89 in 2009. Forecast high: 93
  • Aug. 3 record high: 90 in 1988. Forecast high: 100
  • Aug. 4 record high: 95 in 1993. Forecast high: 97

Is Seattle’s all-time record high of 103 degrees in danger?

Probably not—but it could be close. Most weather models predict that Sea-Tac Airport (where Seattle’s official weather records are kept) will top out right around or just under 100 degrees on Thursday.

However, it’s worth noting that on July 29, 2009—the day Seattle’s current all-time high of 103 degrees was set—most weather models were predicting a max of 101. There does seem to be a propensity for high temperatures to overachieve at Sea-Tac Airport, particularly in the past decade. In light of this, I’ve developed a basic rule of thumb for Seattle’s hottest days: add 2 degrees to the expected high temperature at Sea-Tac to get the actual high. So, a forecast high of 100 degrees for Thursday would likely translate to 102 degrees at Sea-Tac—keeping the 2009 record intact, but just barely.

Stay cool out there!

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