Northwest to cool down following extensive, record-setting heat wave
AccuWeather forecasters say a refreshing change in the weather will progress across the Northwest after a brutal week-long heat wave set numerous records, turned deadly and brought back memories of the heat wave that set all-time record highs in June 2021.
The heat surged to astonishingly high levels in parts of the Northwest. Some of the worst heat occurred in the southern Oregon city of Medford, where the all-time record high temperature of 115 degrees was tied on Friday, July 29, and temperatures eclipsed the century mark for six consecutive days. In Pendleton, Oregon, located in the northeastern part of the state, highs reached the triple digits for a week straight, including back-to-back days in the 110s on Friday and Saturday.
 |
Scorching heat also baked the larger cities along the Interstate 5 corridor. Portland, Oregon, peaked at 102 F on Tuesday and Saturday, and temperatures have reached into the 90s or higher each day in the city since July 23. Sunday was the seventh consecutive day temperatures hit 95 or higher in Portland, a new record for heat of that intensity and duration in the city.
In Seattle, Sunday's high of 95 F narrowly broke the previous daily record set in 2015, and the heat wave was the longest on record there. Sunday's high marked the sixth-straight day on which the temperature peaked at 90 degrees or higher in the city. The previous record for consecutive days of 90-degree temperatures in Seattle was five from July 1-5, 2015, and Aug. 7-11, 1981.
The sizzling heat likely contributed to multiple fatalities. In Oregon, at least seven people were suspected to have died from hyperthermia since the heat wave began last week, The Associated Press reported. Cooling centers were open throughout the Northwest to help people seeking relief. About 250 people stayed overnight in cooling centers in Portland this past Friday, according to the AP.
 |
A sign showing that a cooling center at the Charles Jordan Community Center is open is shown in Portland, Ore., Tuesday, July 26, 2022. (AP Photo/Craig Mitchelldyer) |
During last year's historic heat wave, Seattle set an all-time high temperature of 108 on June 28, while Portland established an all-time high of 116 on the same date.
AccuWeather forecasters say the excessive heat is coming to an end in the Northwest and those in the region will be able to enjoy some cooler weather this week. High temperatures this past weekend were 10 to 20 degrees above normal, but Monday's highs were within 5 degrees of the average in most locations near the coast.
Seattle recorded a high temperature of 81 degrees Fahrenheit, which was its coolest day in over a week and only two degrees above average. Portland still experienced a warm day, with a high of 89, but this felt much cooler when compared to recent conditions.
Locations farther inland needed to wait until Tuesday to break out of the heat spell. Spokane, Washington, reached 97 degrees on Monday, with residents in Boise, Idaho, experiencing their seventh straight day above 100, when the mercury soared to 102 degrees.
 |
The cooldown will continue along the coast and expand inland over the course of the week.
"The persistent heat dome over the West Coast, which has been responsible for this week of extreme temperatures, will finally push into the Plains and eventually the eastern U.S. and take the heat with it," AccuWeather Meteorologist Lauren Hyde explained. "While the change may not be immediate to the east of the Cascades, this will help the jet stream slide southward and usher in cooler air."
 |
On Tuesday, the cooldown encompassed more of the region. In Seattle, temperatures stayed in the upper 70s with a high of 77, with Portland peaking at 88. In Spokane, highs struggled to hit 90 degrees, only doing so during the 4 p.m. PDT hour, a stark comparison to the four consecutive days above 100 that ended Sunday.
Temperatures are likely to drop even more by midweek. In Seattle, forecasters say it isn't entirely out of the question that temperatures fail to reach 70 on Thursday. This would be the coolest weather since July 3, when the high was only 58 degrees.
While temperatures will take a plunge, a surge of moisture associated with the North American monsoon will reach northward, bringing an increase in showers and thunderstorms to the area. This is the same moisture that led to flash flooding in downtown Las Vegas and turned dry riverbeds in Arizona into raging torrents of muddy water.
"People spending a lengthy time outdoors will want to stay aware of the flooding hazard, which can seemingly develop out of nowhere as waters rise in a span of minutes. Even if your exact location isn't seeing rain, runoff from a nearby storm can cause water levels to rise almost instantly," Hyde cautioned.
The pattern change may also enhance the spread of wildfires in areas that stay dry. Some thunderstorms, especially those on the periphery of the threat area, can produce only light rainfall at ground level. When lightning strikes in these dry areas, fires can start and rapidly spread. Thunderstorms can also produce erratic and gusty winds, which can spread fires quickly and make them difficult to contain.
 |
This has been the case with the McKinney Fire in Northern California, which has grown to over 50,000 acres and forced hundreds of evacuations near Yreka, California, a city located about 20 miles from the Oregon border. Much of this may be worsened by ongoing drought conditions in portions of the Northwest. According to the U.S. Drought Monitor, 66 percent of Oregon and 45 percent of Idaho are experiencing drought conditions, while other areas are also drier than average.
The cooler weather is likely to continue for most of the week, but forecasters say there are some indications that this weekend may bring a return to warmer, drier weather in the Northwest.
Correction: This story previously misstated the suspected cause of death of seven individuals in Oregon. The cause of death was hyperthermia, not hypothermia.
Want next-level safety, ad-free? Unlock advanced, hyperlocal severe weather alerts when you subscribe to Premium+ on the AccuWeather app.AccuWeather Alerts™ are prompted by our expert meteorologists who monitor and analyze dangerous weather risks 24/7 to keep you and your family safer.
