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Nearly 40 million Americans are on heat alert Tuesday as two zones of excessively high temperatures sear parts of the Lower 48. Parts of the Southern Plains from Texas to southern Missouri continue to boil as they have most of the summer. But for the Pacific Northwest, the arrival of that sweltering heat comes as more of a shock after what has been a relatively cool summer so far.
Temperatures across the Pacific Northwest are expected to be the highest of the summer and not drop until the weekend. In Seattle and Portland, this heat wave could be near records for longevity. Both cities are under heat warnings until Thursday evening. In Seattle, mercury could hit 90 for four straight days through Friday, while afternoon temperatures in Portland could be near 100.
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The National Weather Service issued heat warnings for millions on Tuesday as the Biden administration unveiled Heat.gov, “a new website designed to provide the public and decision-makers with clear, timely, and science-based information to understand and reduce health risks.” from extreme heat.”
The Pacific Northwest heatwave comes just over a year after Seattle and Portland broke records with high temperatures of 108 and 116 degrees, respectively. The same event set a record high in Canada, where Lytton, British Columbia rose to 121 degrees. The next day the city burned down to the ground.
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Forecasters in Seattle and Portland emphasized that while this year’s heatwave is not nearly as intense as last year, it is characterized by its longevity.
“It’s the duration that’s really remarkable for this event,” said Colby Neuman, meteorologist with the Portland National Weather Service. “Most consecutive 95-degree days in Portland on record is six, and we will certainly be in the race to approach, tie, or surpass that record. In the next few days we will be around 100.”
Portland International Airport hit 98.6 degrees Monday, and after a predicted high of 101 degrees on Tuesday, the city is expected to be in the upper 90s by Friday. The projected high on Saturday is 95 degrees. Currently, the city is forecast to tie the record.
“If we’re seeing highs around 100, heat-related illness hospital visits are definitely much higher than background levels,” Neuman said. “And with Covid still around, hospital capacity is limited and these events are exacerbating that.”
Access to air conditioning is a complicating factor that increases risk in vulnerable populations such as the elderly and homeless. In Portland, 78 percent of homes have air conditioning, but that number drops to 44 percent in Seattle.
Seattle made it to 85 degrees Monday — the average high this time of year is 79 degrees — but any day through Friday should peak at or just above 90 degrees. Heat waves, defined as intervals of three consecutive days of 90 degrees or more, are somewhat rare in Seattle; This is only the 24th since World War II. Half of these heat waves have occurred in the past 15 years, underscoring the role of human-caused climate change in the frequency and intensity of heat runaways.
Officially, the longest record length of a heat wave in Seattle is five days, which occurred in both 2015 and 1981.
“Take extra precautions when working or spending time outdoors,” the Seattle Weather Service said. “If possible, move strenuous activities to early morning or evening.”
The agency drew attention to the Washington public service hotline, available at 2-1-1, which can provide callers with information about cold storage housing and other services.
Of particular concern are elevated night-time temperatures, which keep homes uncomfortably warm without air conditioning. Temperatures in Seattle briefly dipped below 70 degrees on Tuesday morning.
No relief from the heat. Sea-Tac’s temperature fell below 70°C at around 4:50 am and had already risen to 70°C at 6:25 am. pic.twitter.com/73RfaNgXtM
— NWS Seattle (@NWSSeattle) July 26, 2022
In Portland, the low temperature on Tuesday was 69 degrees.
“A large portion of the population here doesn’t have air conditioning,” Neuman said. “In the past, people relied on opening their windows to cool their homes. This time they can’t.”
By the end of the week, the most extreme heat will occur on Thursday and Friday in eastern Washington, where highs could exceed 110 degrees, particularly in the Columbia River Basin lowlands.
Kennewick, Washington, about 50 miles east-southeast of Yakima, could rise to 112 degrees on Thursday and 110 degrees on Friday. Yakima himself will be flirting with 110 degrees on Thursday before dropping to 108 on Friday and 105 on Saturday.
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Temperatures in the 100 to 110 degree range are common in interior and northern Oregon. Medford hit a record high of 107 degrees Monday, while Dallesport, Washington, on the Oregon border, rose to a record high of 108 degrees.
The heat stems from a high-pressure ridge, or “heat dome,” parked in the northeast Pacific west of British Columbia. It deflects the jet stream north toward Canada along with inclement weather and storms. Instead, the Pacific Northwest’s weather is characterized by clear skies and hot, sinking air.
Jason Samenow contributed to this report.