MY, that was warm.
With summer officially beginning only days earlier, an unprecedented "heat dome" set up over the northern Oregon border for the last week of June – beginning with cloudless skies and rapidly cranking up sizzling, almost unbelievable, desert-like summer heat.
We don't really need to remind you of the unprecedented temperatures for Portland posted by the National Weather Service (NWS) Portland office at the airport, because you probably remember them only too well! But, for the record:
June 25: 94°
June 26: 108° (breaking our old all-time record of 107°)
June 27: 112° (breaking yesterday's all-time record of 108°)
June 28: 116° (peaking at 5:02 p.m., breaking yesterday's all-time record of 112°)
June 29: 92°
That 116° reading was the second-highest temperature recorded in the entire United States on June 28 – second only to the 117° reading 45 miles south, in Salem!The landmark heat wave finally broke shortly after the peak of 116° on Monday, June 28, when a shift of the east wind around to the west brought in cooler coastal air, and a drop of over 25 degrees in less than three hours.
By Tuesday, June 30, the daily high was a pleasant 78°; and for many days afterward Portland did not even touch 90. But the damage was done, and in a city where many people have not yet invested in air conditioning, dozens of deaths were attributed to the three days of heat, which also singed many trees and plants, turning green foliage brown.
'Heat Dome' blamed for temperatures
Although summer officially began on June 20, temperatures usually don't rise to uncomfortable levels (the 90's) until August or September. And never in local records have they ever risen even close to the record-breaking temperatures recorded June 26-28.
To learn more about what caused this unprecedented heat wave, we turned to NWS Meteorologist Rebecca Muessle: "You've probably heard the term 'heat dome', used to describe the unseasonably warm temperatures we've experienced over the past few days.
"One can think of a 'heat dome' as the total opposite of a winter 'polar vortex'. Instead of a low barometric pressure center bringing in cold air from the north, the 'heat dome' is a high pressure center that builds up over the area," Muessle told THE BEE.
"Usually, the ground at lower elevations will warm under clear skies during long summer days – but it's moderated by cooler temperatures aloft at, say, 5,000 feet," Muessle explained. "But, with hot air moving from the desert southwest up into Oregon, Washington, and British Columbia, the area above us of hot air was very deep; giving us a 'double-whammy' of warm air."
In addition, the meteorologist added, there was a "thermal low" off the coast, delaying cooler marine airflows from dislodging the heat bubble. "Because the onshore westerly flow wasn't there, we saw very little reprieve for three days," Muessle said.
A sweltering summer?
The National Weather Service's three-month outlook, issued on June 17, predicted "above normal temperatures" for most of the west.
"Our probability of warmer-than-typical temperatures over the summer is about 40% –partly due to the fact we're already seeing warm temperatures," explained Muessle. "But, this early onset of record high temperatures and the warmer trend does not mean we'll be revisiting these record temperatures all summer long!"By the way, had that little low-pressure system not finally arrived west of Portland on June 28, we now know what our high would have soared to on Tuesday the 29th, and it was truly scary. The little British Columbia town of Lytton, 40 miles northeast of Vancouver B.C., had been within a degree of Portland on each of our three record-setting days – but that little low pressure system took another day to get up there and start cooling things down. On Tuesday, June 29, Lytton in British Columbia soared to 121 degrees Fahrenheit, which is now officially the hottest temperature ever recorded in Canada. So, but for that welcome little low pressure system arriving on the coast, Portland would have reached 121 or 122 degrees on Tuesday! Instead, it was 93 degrees here – and was the last 90-degree day in the first half of July. The casualties among people and vegetation from experiencing over 120 degrees here can only be imagined. By comparison, the highest daily temperature ever reliably recorded anywhere in the entire world is 134 – and it was at aptly-named Death Valley, California. Portland would have been within a dozen degrees of that on Tuesday, had not the weather broken Monday night. THE BEE suggests that may be time for us all to consider installing air conditioning!
To check Portland's current weather and the seven-day forecast, you can always go online – tinyurl.com/ct474n3j
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