Seattle beat the record high for Aug. 5 - hitting 93 degrees. The previous record at Sea-Tac was 89, set in 1977.
Also on Sunday, Olympia hit 94 and Bellingham was 85 degrees.
On Monday, temperatures will cool by 10-15 degrees.
KING 5 Meteorologist Jim Guy says an upper air disturbance is moving north out of California today and should move through the area late tonight into Monday morning.
"That could trigger some showers and thunderstorms mainly over the Cascades," he said. "However, we do have a slight chance of a shower or thunderstorm in the morning over the Puget Sound area."
But it doesn't look like we'll see much rain as the system moves through.
Expect temperatures in the mid-70s to near 80 on Monday.
Another push of marine air arrives on Wednesday with morning clouds and afternoon sunbreaks and highs in the mid-70s.
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Temperatures in the 90s bring the risk of heat exhaustion and heat stroke. Be sure to take care of yourself and your pets. Forecasters also are advising people who cool off in lakes and rivers to wear life jackets.
The Puget Sound Clean Air agency has warned that unhealthy smog could build up for communities against the Cascade Mountains.