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Nearly 40 million Americans are under heat alerts Tuesday as two areas of excessively high temperatures roast portions of the Lower 48. Parts of the southern plains, from Texas to southern Missouri, continue to bake as they have most of the summer. But for the Pacific Northwest, the arrival of this sweltering heat is more of a shock after a relatively cool summer so far.
Across the Pacific Northwest, temperatures are expected to be the hottest of the summer and aren’t expected to drop until the weekend. In Seattle and Portland, this heat wave could approach longevity records. Both cities are under extreme heat warnings until Thursday evening. Seattle could see the mercury reach the 90s for four straight days through Friday, while Portland could see afternoon temperatures near 100.
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The National Weather Service issued heat alerts for millions of people on Tuesday as the Biden administration unveiled Heat.gov, “a new website to provide the public and decision makers with clear, timely and data-based information in science to understand and reduce the health risks of extreme heat.”
The heat wave in the Pacific Northwest comes a little more than a year after all-time records were broken in Seattle and Portland, with high temperatures of 108 and 116 degrees, respectively. That same event set a record high in Canada, where Lytton, British Columbia soared to 121 degrees. The next day, the town burned down.
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Meteorologists in Seattle and Portland noted that this year’s heat wave, while not as intense as last year’s, is notable for its longevity.
“It’s the length that’s really remarkable for this event,” said Colby Neuman, a meteorologist with the National Weather Service in Portland. “The most consecutive 95-degree days on record in Portland is six, and we’ll certainly be in the running to approach, tie or break that record. The next few days, we’ll be right around 100.”
Portland International Airport hit 98.6 degrees on Monday, and after a predicted high of 101 degrees on Tuesday, the city is expected to be in the 90s through Friday. The expected high for Saturday is 95 degrees. Currently, the city is expected to break the record.
“When we see highs around 100, hospital visits with heat-related illnesses are definitely much higher than background levels,” Neuman said. “And with covid still around, there’s a limit to hospital capacity, and these events exacerbate that.”
Access to air conditioning is a complicating factor that amplifies risk in vulnerable populations such as the elderly and the homeless. In Portland, 78% of homes have air conditioning, but that number drops to 44% in Seattle.
Seattle hit 85 degrees on Monday (the average high for this time of year is 79 degrees), but each day through Friday should reach 90 degrees or slightly above. Heat waves, defined as intervals of three consecutive days of 90 degrees or higher, are somewhat rare in Seattle; this will mark only the 24th since World War II. Half of these heat waves have occurred in the past 15 years, highlighting the role of human-caused climate change in making atypical heat events more frequent and intense .
Officially, the longest heat wave duration in Seattle is five days, which occurred in both 2015 and 1981.
“Take extra precautions if you work or spend time outside,” the Seattle Weather Service said. “When possible, shift strenuous activities to early morning or evening.”
The agency called attention to Washington’s public service hotline, accessible at 2-1-1, which can provide callers with information about cooling shelters and other services.
Of particular concern are the high nighttime temperatures, which will keep homes without air conditioning uncomfortably hot. Temperatures in Seattle briefly dipped below 70 Tuesday morning.
No relief from the heat. The temperature at Sea-Tac dropped below 70° around 4:50am and is back up to 70° by 6:25am pic.twitter.com/73RfaNgXtM
— NWS Seattle (@NWSSeattle) July 26, 2022
In Portland, the low temperature Tuesday was 69 degrees.
“There’s a large portion of the population here that doesn’t have air conditioning,” Neuman said. “In the past, people relied on opening windows to cool their homes. This time they can’t.”
Through the end of the week, the most extreme heat will occur Thursday and Friday in eastern Washington, where highs could exceed 110 degrees, especially in the lowlands of the Columbia River Basin.
Kennewick, Wash., about 50 miles east-southeast of Yakima, could top 112 degrees Thursday and 110 on Friday. Yakima proper will flirt with 110 degrees Thursday before a relative cooldown to 108 on Friday and 105 by Saturday.
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Temperatures between 100 and 110 degrees will be common across inland and northern Oregon. Medford tied a record high of 107 degrees on Monday, while Dallesport, Wash., on the Oregon border, soared to a record high of 108.
The heat is coming from a ridge of high pressure, or “heat dome,” that is stationed in the Pacific Northeast west of British Columbia. It is diverting the jet stream north towards Canada along with the inclement weather and the storm. In contrast, the climate in the Pacific Northwest is characterized by clear skies and warm, sinking air.
Jason Samenow contributed to this report.