Dangerous heat wave unfolding in Pacific Northwest, Western Canada
A spring heat wave is building across the Pacific Northwest, and AccuWeather forecasters say that many cities and towns, including Seattle, could end up having their first 90-degree days of the year.
The warmth, courtesy of a building area of high pressure over the western United States, will allow afternoon high temperatures to reach 15 to 25 degrees Fahrenheit (8 to 14 degrees Celsius) above historical averages from California to areas north into western Canada into the new week.
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Ahead of the warmup, heat advisories were issued in parts of the western U.S. by the National Weather Service, while its Canadian equivalent, Environment Canada, issued special heat statements in portions of Alberta, British Columbia and Saskatchewan.
The rising temperatures are a sudden pattern change across the region, where temperatures had been largely below historical averages at the start of May.
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"It will feel like Mother Nature flipped a switch as the jet stream bulges northward across the Western states," said AccuWeather Meteorologist Mary Gilbert.
From May 1-10 in Portland, all but three days featured temperatures at or below historical averages, which are in the upper 60s at this point. However, a period of exceptional warmth began Friday, as the mercury touched the 90-degree mark for the first time this year and broke the 1973 daily record of 87. Record-challenging highs in the lower 90s are expected to persist right into Monday.
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"Typically, Portland encounters its first reading of 90 or higher in the middle of June. The earliest day on record above 90 degrees for the area occurred May 6, 1987," said Gilbert.
Portland reached a second consecutive daily record high on Saturday, breaking the 1973 record of 92 by a single degree.
Seattle's temperatures had been similarly cool to start May but will also camp out in the 80s into Monday, which is about 20 degrees above historical averages in the mid-60s. Seattle also set a daily record high on Saturday, reporting a high of 86 that topped the old record of 85 from 2018.
The prospects for a 90-degree day in the Emerald City are lower compared to Portland, but the chance is not zero on Sunday, forecasters say.
"Currently, the earliest 90-degree day on record for Seattle is May 17, 2008," added Gilbert. A 90-degree reading on Sunday would rewrite the record books there. In fact, there are typically only two 80-degree or higher days in Seattle in an average May, a mark that Seattle has already tied with over half of the month of May remaining.
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Daily record high temperatures are also in jeopardy for a bevy of cities. Portland could string together a three-day stretch of record-breaking temperatures through Sunday.
In Seattle, Friday's high of 82 F broke a daily record that stood since 1959, and records through Sunday are in serious danger of falling as well.
Underlining the historical nature of this magnitude of heat this early in the season, averages in the heart of summer do not even climb to the level of heat expected into early week. In Portland, historical average high temperatures top out in the mid-80s in late July and early August, while they top out in only the upper 70s in Seattle around the same time.
Because temperatures this high and this early in the year are unusual, residents should take precautions to guard against heat-related illnesses by staying hydrated and avoiding spending a prolonged time outdoors during the peak heating of the day.
The heat is intense for this time of year in the Pacific Northwest, but experts say that temperatures will still fall well short of the extraordinary, all-time record highs set back in the summer of 2021. In late June of that year, Portland hit an all-time record of 116 F, while Seattle set an all-time record of 108.
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Locations as far south as California's San Joaquin Valley will also bask in early-season warmth into early this week, with cities such as Bakersfield and Fresno reaching into the middle and upper 90s each afternoon.
Western Canada, already beleaguered from dry conditions that have helped fuel massive wildfires in the province of Alberta, will be unusually warm into this week as well. Vancouver, British Columbia, could reach its earliest 80-degree-Fahrenheit (27-degree-Celsius) day on record early this week; the current record for the earliest date of that occurrence is May 16, 2006.
For those hoping for a return of cooler, more seasonable weather, AccuWeather forecasters expect the warmth to wane some early this week, as clouds and a chance of showers and thunderstorms return to the region. Despite that, the mercury should still continue to run a few degrees above historical averages in most areas through all of this week.
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