Across the Pacific Northwest, temperatures are expected to be the highest of the summer and not expected to drop until the weekend. In Seattle and Portland, this heatwave could approach longevity records. Both cities are under excessive heat warnings through Thursday evening. Seattle could see the mercury hit 90 for four straight days through Friday, while Portland could have afternoon temperatures approaching 100.
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The National Weather Service issued heat alerts for millions on Tuesday as the Biden administration unveiled Heat.gov, “a new website to provide the public and policymakers with clear, timely, science-based information to understand and reduce health risks from extreme heat.
The Pacific Northwest heatwave comes just over a year after all-time highs were broken in Seattle and Portland, with high temperatures of 108 and 116 degrees, respectively. That same event set a record in Canada, where Lytton, British Columbia soared 121 degrees. The town was burned down the next day.
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Forecasters in Seattle and Portland pointed out that this year’s heat wave, while not as intense as last year, stands out for its longevity.
“It’s the duration that’s really remarkable for this event,” said Colby Neuman, a meteorologist with the National Weather Service in Portland. “The record number of consecutive 95-degree days in Portland is six, and we will definitely be in contention to approach, match or exceed that record. The next few days we will be just 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 upper 90s through Friday. The maximum predicted for Saturday is 95 degrees. At present, the city is expected to tie the record.
“When we see highs around 100, hospital visits for heat-related illnesses are definitely much higher than background levels,” Neuman said. “And with covid still present, there is a limit to hospital capacity, and these events are exacerbating that.”
Access to air conditioning is a complicating factor that amplifies the risk in vulnerable populations such as the elderly and the homeless. In Portland, 78% of households have air conditioning, but that number drops to 44% in Seattle.
Seattle hit 85 degrees on Monday — the average high this time of year is 79 degrees — but every day through Friday is expected to peak at or just above 90 degrees. Heat waves, defined as intervals of three consecutive days of 90 degrees or more, are fairly rare in Seattle; it will only be the 24th since World War II. Half of these heat waves have occurred in the past 15 years, underscoring the role of human-induced climate change in the proliferation and intensity of aberrant heat episodes.
Officially, the longest record duration for a heat wave in Seattle is five days, which occurred in both 2015 and 1981.
“Take extra precautions if working or spending time outdoors,” the Seattle Weather Service said. “If possible, reschedule strenuous activities to early morning or evening.”
The agency drew attention to the Washington Public Service telephone hotline, reachable at 2-1-1, which can provide callers with information about cooling shelters and other services.
A particular concern is high nighttime temperatures, which will keep accommodations without air conditioning warm. Temperatures in Seattle briefly dipped below 70 on Tuesday morning.
In Portland, the low temperature on Tuesday was 69 degrees.
“There’s a lot of the population here that doesn’t have air conditioning,” Neuman said. “In the past, people relied on opening their windows to cool their homes. They can’t this time.
Through the end of the week, the most extreme heat is expected 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 soar to 112 degrees Thursday and 110 Friday. Yakima proper will flirt with 110 degrees on Thursday before a relative loosening to 108 on Friday and 105 on Saturday.
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Temperatures in the 100 to 110 degree range will be common in interior and northern Oregon. Medford tied a record 107 degrees on Monday, while Dallesport, Wash., on the border with Oregon, hit a record 108.
The heat is coming from a high-pressure ridge, or “heat dome,” that sits in the Pacific northeast west of British Columbia. It deflects the jet stream north towards Canada, along with bad weather and storms. Instead, the weather in the Pacific Northwest is characterized by clear skies and warm, descending air.
Jason Samenow contributed to this report.