Updated

The Pacific Northwest is in for a potentially historic and life-threatening heat wave through the weekend.

While much of the Western U.S. has felt the impact of dangerous temperatures over the last couple of weeks, Northwestern states were not yet subject to the heat wave's full force.

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Even as blazes burned – and continue to burn – in Washington state and Oregon, temperatures spiked at the beginning of the week.

Since then, the National Weather Service (NWS) offices in both states have warned residents of record-breaking highs.

On Monday, the NWS in Seattle reported that the SeaTac daily record high temperature set in 1992 had been tied. SeaTac is a city surrounding the Seattle–Tacoma International Airport.

The agency's Portland, Oregon, account claimed Thursday that the upcoming heat wave would be an "unprecedented event," breaking several daily, monthly and possibly all-time records.

NWS Seattle cautioned that Sunday could be up to 29 degrees hotter than normal during the "significant event," noting Thursday that the normal high through the weekend in Seattle would likely be 80 degrees or higher through "at least the 4th of July."

The NWS Weather Prediction Center said Thursday that an upper-level ridge would move over the Northwest on Saturday and aid in producing high temperatures from the upper 90s to low- and mid-100s.

Additionally, there are excessive heat warnings and excessive heat watches – in addition to red flag warnings – over the Northwest and Northern California.

Forecaster AccuWeather said Thursday that residents of Portland could see highs of more than 110 degrees Fahrenheit and Seattle would feel blistering temperatures of around 30 to 40 degrees above normal.

In response, Seattle Mayor Jenny Durkan issued a reopening of public spaces used to stay cool. 

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"This upcoming week, we’re reopening many City facilities for individuals to stay cool, but many of our City’s indoor spaces remain closed or at reduced capacity due to state and local Public Health mandates," Durkan said in a press release. "As a reminder, drink plenty of water, reduce strenuous outdoor activities, check on neighbors and those at risk for heat-related illness, and don’t leave any pets in the car."

Portland Mayor Ted Wheeler wrote on Twitter Thursday that cooling centers would be open for 24 hours beginning of Friday at 1 p.m. PT.