Seattle's high was 97 Tuesday, tying a record set in 1997 while Olympia recorded 101, exceeding its previous high of 100, CNN reports.
In Oregon, Portland hit 106 degrees Tuesday, Salem was 107 and Medford was 108, all breaking previous temperature records.
"It was particularly unpleasant last night," says University of Washington meteorologist Cliff Mass.
Mass told the Seattle Times the current heat wave is going to be historic.
"We're really not prepared for it," Mass says. "Most homes don't have air conditioning and a lot of stores don't."
The current forecast called for temperatures to peak Wednesday and then slowly decline.
The National Weather Service says temperatures could drop to the high 80s by Saturday.