If not for sporadic flashes of leaves turning red and gold, the first week of astronomical fall felt more like summer than autumn.
A surge of late September heat pushed mercury readings to 10-20 degrees above normal across the Inland Northwest and most of Washington state. With high temperatures soaring into the upper 80s and even low 90s in our region, some might have wondered if Mother Nature planned to skip the gradual cooldown of fall and jump directly from summer to winter.
The hottest temperatures arrived on Tuesday with Spokane, Pullman, Clarkston and Lewiston reaching a high of 90 degrees and LaCrosse, 91.
All of which makes it hard to believe that three years ago this week, record-breaking snow fell across parts of the Inland Northwest and late-season tomatoes froze off their vines. On Sept. 28, 2019, Spokane received 1.9 inches of snow followed by another 1.3 inches the next morning. The high temperature reached only 38 degrees, and the overnight low hovered in the mid-20s. Not surprisingly, the growing season came to an abrupt end.
What caused these two unusual, yet opposite, weather patterns to occur?
Three years ago, an incoming storm system collided with a thrust of arctic air to produce winter-like weather. This week, a ridge of high pressure centered over the Desert Southwest shape-shifted northward to include the Pacific Northwest, bringing hot, dry, sinking air with it.
Last year at this time, conditions were much more variable. Highs ranged from 58 to 77 degrees and overnight lows between 41 and 55 degrees. What’s more, the region received measurable rainfall on three days, including 0.36 inches on Sept. 27 in Spokane.
Getting back to this year’s September sizzle, a fall cold front that arrived Tuesday night will lower temperatures into the mid-60s Thursday – considered normal for this time of year – and bring some clouds and a chance of rain.
But normal won’t last. A bright sun, blue skies and above-average temperatures are expected to return this weekend and into early next week. Highs are expected to run in the mid- to upper 70s.
All the while, the season’s last garden tomatoes will continue to ripen.
Nic Loyd is a meteorologist in Washington state. Linda Weiford is a writer in Moscow, Idaho, who’s also a weather geek. Contact: firstname.lastname@example.org.
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