Pacific Northwest Bakes in Record-Setting Heat Wave

A heat dome has enveloped the Pacific Northwest, driving temperatures to extreme levels — with temperatures well above 100 degrees — and creating dangerous conditions in a part of the country unaccustomed to oppressive summer weather or air-conditioning.

One of the hottest cities in the region on Monday was Salem, Ore., about 45 southwest of Portland, where it reached 116 degrees in the afternoon, a record for the city, the National Weather Service said.

At Portland International Airport in Oregon, it reached 115 degrees on Monday, after it had reached 112 degrees on Sunday. The high on Monday in Portland was the highest temperature ever recorded there since historical records began in 1940, the National Weather Service said.

The average high temperature for this time of year at the airport is about 73 degrees, said forecasters.

On Monday, Seattle broke a record for the highest temperature ever recorded by the National Weather Service there: 107 degrees. The previous high of 105 degrees had been set in July 2009.

“Goodnight cruel sauna — I mean, Seattle,” Maddie Kristell, a meteorologist for the National Weather Service in Seattle, wrote on Twitter on Saturday night, along with a photo of two air-conditioning units that she had running.

The National Weather Service issued excessive heat warnings on Monday for much of Washington and Oregon, as well as for sections of California, Idaho and Nevada.

Last month the National Oceanic and Atmospheric Administration adjusted its “climate normals,” baseline data of temperature, rain, snow and other weather variables collected over three decades at thousands of locations across the country.

“We’re really seeing the fingerprints of climate change in the new normals,” Michael Palecki, who manages the project at NOAA’s National Centers for Environmental Information, said when the normals were updated.

Last year tied 2016 as the hottest year on record, as global temperatures continued their relentless rise brought on by the emission of heat-trapping greenhouse gases.

The warning for much of Oregon and Washington, where state and local entities opened cooling centers, will remain in effect until Monday night.

The meteorological anomaly in the Pacific Northwest, which forecasters attributed to an upper-level ridge of high pressure stalled over British Columbia, even led the National Park Service to warn hikers about snow and ice are melting faster than normal on Mount Rainier in Washington.

“Even higher elevations such as Paradise won’t escape the extreme heat hitting the PNW,” the national park said on Twitter.

The heat is expected to linger in areas farther east until at least the middle of the week, according to the National Weather Service. Its forecast office in Spokane, Wash., predicted high temperatures of at least 112 degrees from Sunday through Wednesday.

In preparation for the heat wave, Gov. Jay Inslee of Washington suspended limits on the number of people who could be accommodated at cooling centers run by the government and by nonprofit groups in the state.

The limits had been put in place as part of public health emergency orders during the coronavirus pandemic.

The Seattle Library said on Sunday morning that it was opening additional air-conditioned branches on Sunday and Monday to provide people refuge from the heat.

The Oregon Health Authority announced on Friday that it had also lifted limits on the number of people who could gather at swimming pools, movie theaters and shopping malls.

At the Holiday Inn Express & Suites in North Seattle, the television station KING 5 reported that the hotel’s air-conditioned rooms were fully booked this weekend, the first time since the pandemic began.

“It’s been a blessing,” Ron Oh, the hotel’s general manager, told the station.

Mr. Oh, who is also the board chairman of the Washington Hospitality Association, said the phone was ringing constantly with questions about room availability.

“It generally comes down to, ‘Oh, my God, it’s so hot, I need a place with air-conditioning,’” he said.

Heather Murphy and Jesus Jimenez contributed reporting.