Seattle area’s ‘insane’ heat wave finally gives way to cooler weather

Temperatures have already begun to cool across the Puget Sound region, after a record-shattering heat wave swept across over the last three days.

The Seattle area reached triple digits for the third day in a row on Monday, hitting 108 degrees and officially making it Seattle’s hottest ever day in its history. Prior to this last week, the city had never seen consecutive 100-degree days.

The Great Cooldown

An Excessive Heat Warning will remain in effect until Tuesday evening, but forecasters have said Tuesday itself will be about 20 degrees cooler across the Puget Sound.

👀 Can you spot the marine push? Marine stratus has started to move inland this evening, cooling areas along the coast and across SW interior by 30 degrees in some places. #wawx pic.twitter.com/UdFYSkttqc

— NWS Seattle (@NWSSeattle) June 29, 2021

According to the NWS, the cooler marine air is moving up north from the coast. In fact, Westport dropped from 83 to 64 late Monday morning. Shelton went from 106 degrees at 7 p.m. to 75 by 9:30 p.m.

In the Seattle area, overnight temperatures at long last dropped into the 60s, after sitting around a sweltering 80 degrees on Sunday night. By Tuesday morning, temperatures were between 10 and 25 degrees cooler than they were the previous day at the same time.

Temps this AM remain roughly 10-25 degrees cooler than this time yesterday. Thanks to western WA's natural A/C…the marine push! Some locations are only running 5 to 10 degrees cooler today…but there's good news…another marine push moves inland tonight! #wawx pic.twitter.com/CHktAkDq91

— NWS Seattle (@NWSSeattle) June 29, 2021

While temperatures are expected to eventually end up in the low 90s Tuesday, the recovery period is why the NWS extended the Excessive Heat Warning to Tuesday night.

“It is imperative that heat-related precautions are not just automatically neglected,” the NWS wrote in its Forecast Discussion. “Heat-related impacts are likely to carry over given that there won’t be an extended period of cooler temperatures to fully recover from the extreme heat of the past few days.”

Wednesday will present more cooling, according to the NWS. Interior locations will see highs in the mid 80s. Areas near the water and high elevations should remain in the upper 60s and low 70s. Thursday will see similar patterns.

Records and such

Temperatures in Seattle crested 100 degrees shortly before 4 p.m. on Saturday, and then again on Sunday just after 2 p.m., reaching 104 degrees, and at the time, setting the city’s all-time record for its hottest ever day. Monday broke that record at 108 degrees around 6 p.m.

Other areas broke all-time records on Monday (according to the National Weather Service):

• Dallesport 118 degrees
• Seattle (Sea-Tac) 108 degrees, previously 104 on June 27, 2021
• Bellingham 99 degrees, previously 96 on July 29, 2009
• NWS Seattle 107 degrees, previously 105 on July 29, 2009
• Olympia 109 degrees, previously 105 on June 27, 2021
• Quillayute 110, previously 99 on Aug. 9, 1981

The record high of 110°F at Quillayute didn't just barely break the previous high, but shattered it by surpassing the previous highest temperature by 11 degrees! Yesterday's record at Hoquiam was similarly remarkable, setting a new mark by 8 degrees! (Map via @Climatologist49) pic.twitter.com/Oi1NG3iHLf

— NWS Seattle (@NWSSeattle) June 29, 2021

The NWS also noted Monday that Dallesport’s high of 118 was “preliminary.” If it gets certified, it would tie the record for the hottest ever day in Washington’s history.

Overall, it marks a period that University of Washington climatologist Cliff Mass described as “simply insane,” as the region suffered through a period of “unparalleled highs.”

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