The cool marine layer that blew in early Wednesday might have some wondering whether the forecast for upcoming 100-degree weather is still correct.

It is.

And on top of warm days forecast for the Puget Sound area, conditions could be made even more intense by the predicted overnight lows, which could break the all-time record of 71 degrees set on July 29, 2009.

That stifling night followed the area’s hottest day so far, 103 degrees recorded at Seattle-Tacoma International Airport.

Mary Butwin, a meteorologist with the National Weather Service in Seattle, said our cooling clouds will take a while to burn off, but burn off they will.

“It’s going to be a slow one, but we will start the real warm-up tomorrow,” she said midmorning Wednesday. “And by the weekend I’m going to go ahead and say it’s going to be hot. Very hot.”

How hot? It’s expected to reach 100 degrees at Sea-Tac on Sunday, she said, with overnight lows of 70 degrees both weekend nights.


“Saturday and Sunday could both be [overnight low] June records and could be all-time records as well,” Butwin said.

On Tuesday afternoon, the weather service issued an excessive heat watch for the Seattle area, predicting dangerously hot daytime conditions from Friday afternoon through Monday afternoon. 

With temperatures running so high, Seattle is directing residents to public sites where they can cool off, including library branches, wading pools, spray parks and swimming beaches.