Searing, long-duration heat to target Pacific Northwest
Summer is in full force for much of the United States as dry conditions take hold and sunshine blazes. After managing to avoid the worst Mother Nature has to offer for much of the summer, high heat has taken hold, and AccuWeather forecasters say that more of the same is in the cards this week.
An area of high pressure is set to expand across the Pacific Northwest through much of the week which will make dry and hot conditions the norm for many across the region.
"This high pressure will keep the pattern in place, and ensure that hot weather will continue across the area," cautioned AccuWeather Meteorologist Joe Bauer.
Already, temperatures have reached sweltering levels in some of the Northwest's major cities. In Portland, Oregon, temperatures surged to 99 F on Monday, coming only a single degree shy of the daily record high set in 1988.
To the north in Seattle, the mercury read 87 degrees, the warmest so far this month. The heat was more intense farther inland, with Redmond, Oregon surging to 100 degrees on Monday. Spokane, Washington reach a similarly toasty 95 degrees, while Boise, Idaho topped out at 96 F. At Rogue Valley International Airport in Medford, a reading of 107 was recorded in the late afternoon hours, which ties the daily record set in 1988.
High temperatures will steadily increase by a handful of degrees from Monday into Tuesday across much of the Pacific Northwest and into southern British Columbia, Canada. Around midweek, temperatures are forecast to soar 10-15 degrees Fahrenheit (5-8 C) above normal in many locations.
The magnitude and longevity of the heat will be particularly worrisome in coastal areas, where highs typically range from the mid-70s to the mid-80s. In Seattle, highs will range from the mid-80s to the mid-90s for much of the week. The heat will likely peak on Tuesday and Wednesday. Highs will be near or above 90 each day in Portland, Oregon, through the end of the week, and are even forecast to reach the century mark on Tuesday.
Inland from the coast, heat will remain elevated for a significant duration across a large swath of the Northwest.
For valley cities like Yakima and Omak, Washington, temperatures will top out much higher. For cities in the valleys of Washington and Oregon, the mercury is set to peak in the upper 90s or low 100s F for much of the week. In the valleys, the hottest days of the week are likely to be Wednesday and Thursday.
Medford is forecast to reach between 105 and 110 degrees through Friday and hit at least 100 both days of the weekend, according to the latest AccuWeather forecast.
Despite the severity of the heat this week, it will not come close to the historic, deadly heat wave of June 2021.
It was a little over a year ago that the Northwest set all-time record highs when a blistering heat wave evolved in late June 2021. During that historic weather event, the state record in Washington was set on June 29, 2021, with a high of 120 F in the small community of Hanford in south-central Washington. The Oregon state record of 119, previously set at multiple locations, was tied at Pelton Dam, located about 90 miles southeast of Portland.
People walk near Pike Place Market, Tuesday, June 29, 2021, in Seattle. (AP Photo/Ted S. Warren)
June 2021's heat wave brought extreme temperatures to the coasts of Washington, British Columbia and northern Oregon. Seattle set an all-time record high on June 28, 2021, when the mercury reached 108, while Portland also set an all-time record that day with a temperature reading of 116. Forecasters say the temperatures forecast for much of the coastal Northwest over the week will stop well short of last June's incredibly high marks.
While highs may fall short of records in most locations during the upcoming heat wave in the Northwest, above-average temperatures for a prolonged period of time will put the heat into dangerous territory for some residents and visitors alike.
The potential for dehydration, heat exhaustion and heatstroke will increase dramatically, especially for those partaking in rigorous exercise and manual labor, experts warn. People are urged to drink plenty of fluids and take breaks from the heat when possible.
The coastal Northwest is well short of the national average when it comes to the number of air-conditioned homes in the region. The lack of air conditioning can make dealing with heat waves difficult and even dangerous for some individuals, such as young children, the elderly and those with health issues. Less than half of the homes in Seattle are air conditioned, compared to the national average of 90%, according to USAFacts.org.
As temperatures surge and rainfall chances remain minimal, soil and brush will dry out substantially during the heat wave, according to Bauer.
"The heat wave will dry out fuels as the region enters the peak of the wildfire season," Bauer said.
Spring to early summer rainfall has been average to above average over much of the Northwest. Ample rainfall and temperatures near average have helped keep fuels moist thus far. But that combination has also allowed more grass and shrubs to grow, which can become more sources for wildfire ignition as the vegetation dries out later in the summer.
Monsoon thunderstorms to return to Southwest
Farther south, a different hazard will emerge for the Southwestern states as monsoon moisture surges northward out of Mexico once again. This surge of moisture will set the stage for widespread rounds of daily thunderstorms across portions of California, Nevada, Utah, Colorado, New Mexico and Arizona.
While any rainfall across the incredibly dry region is necessary to combat drought, a handful of risks will arrive with any storms. Due to how dry the ground across the Southwest is, any heavy rainfall will likely quickly overwhelm the ground's ability to soak up moisture. This will likely result in flash flooding at times for portions of the area.
Burn scars from area wildfires are particularly susceptible to flash flooding and can result in dangerous debris flows.
Danger can develop even where heavy rain does not reach the ground due to the possibility of dry lightning. Dry lightning occurs when a thunderstorm produces little-to-no rainfall due to dry air near the surface that causes precipitation to evaporate before it reaches the ground.
Lightning strikes with little-to-no precipitation can easily spark wildfires across the Southwest. Lightning strikes were responsible for 71 percent of areas burned in the United States from 1992-2015, according to the United States Forest Service.
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