Seattle, Portland amid record-setting warm spell
The northwestern United States has had its share of heat waves since early this past summer, and the region is in the midst of another bout of abnormal, record-setting warmth, AccuWeather meteorologists say.
Across much of the nation, average high temperatures tend to drop significantly as the autumn season progresses, and the Northwest is usually no exception. But this fall has been a different story.
In the case of Seattle, for example, the average high temperature typically declines from 66 to 56 from the start of October to the end of the month. Yet, so far this month, temperatures have not abided by the consistent downward trend in much of the Northwest.
"The stretch of warmth has encompassed Seattle and Spokane, Washington; Portland, Oregon; Boise, Idaho, and many other cities during the first half of this month, resulting in observed temperature departures ranging from 6-10 degrees above average," AccuWeather Meteorologist Brandon Buckingham said.
To put that in perspective, a temperature departure of up to 2 degrees above or below average in any part of the country is considered by meteorologists to be within the bounds of normal over a time period from a couple of weeks to a couple of months.
As a stretch of mild and sunny conditions persists across most of the Northwest well into next week, record highs will be challenged on some days in some locations and blown away in others.
Some of the warmest weather in the Interstate 5 corridor will occur through Sunday.
"The high in Seattle could break the current record by 7 degrees on Sunday," AccuWeather Meteorologist and Climatologist Ryan Adamson said. The temperature should peak near 80, while the current daily record of 72 was set in 2018.
This would follow on the heels of Portland accomplishing that very same feat on Saturday, with the high of 87 breaking the old record of 80 from 1991 by seven degrees. Yet another record high of 81 is forecast in Portland on Sunday, which would mark the fifth consecutive day of record heat.
The culprit will be a weather pattern familiar to people in the Northwest since late June.
"A strong area of high pressure is building at both the jet stream level and in the lower part of the atmosphere," AccuWeather Senior Meteorologist Heather Zehr said.
A heat wave in late June and another in late July were both driven by such a pattern. An extreme version of the atmospheric setup in late June 2021 set all-time record highs in a number of locations in the Northwest. That pattern produced widespread highs above 100 degrees.
Even though October sunshine and short days will not support anything close to those temperature levels this time, the persistence of the warmth is rather unusual, forecasters say.
The warmth should not be intense enough to put individuals at a health risk. However, light winds can lead to a buildup of pollutants and worsen air quality, which can cause trouble for sensitive individuals and those with respiratory or cardiac problems, experts say. These conditions can be made worse in areas blanketed by smoke from existing wildfires.
As of Saturday, there were several dozen fires burning from Washington to Oregon, Idaho and western Montana, according to the national Incident Information System.
For most individuals, the weather should bring comfortable conditions and offer an extended period to make preparations for the upcoming winter season.
As the warmth continues into next week in the region, daily record highs dating back to the World War II era could be challenged.
If temperatures reach the mid-70s in Spokane, daily records that are more than seven or eight decades old could be broken. The daily record for this upcoming Tuesday of 76 was set in 1940, and Wednesday’s record of 73 has stood since 1944.
The same weather pattern will also keep rain away from the region.
"A typical October tends to bring an increased amount of storm activity across the Northwest, but this month has been largely bone dry across the region," Buckingham said.
The storm train over the Pacific has remained well to the north so far, rather than progressing southward.
"As a result, wildfire concerns may span a longer duration this fall season," Buckingham said, adding that no extreme fire risk days are expected through the upcoming week as winds will generally remain light.
A dramatic cooldown is not in the immediate offing for parts of the Northwest next week, according to Zehr.
"The core of the warmth will gradually shift eastward next week as high pressure slowly migrates toward the Rockies," Zehr said. However, the high pressure area will still exert enough influence to keep temperatures in the I-5 corridor well above average during much of the week.
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