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Heat signals swept across the Pacific Northwest on Friday, with 11 million people under extreme heat warnings, including residents of Seattle and Portland. Another 12 million are under heat warnings as temperatures spend at least another day peaking around dangerous levels.
This is a prelude to an even greater accumulation of heat waves across the rest of the Lower 48, bringing hot conditions across much of the Plains, Midwest and Corn Belt as the calendar turns to August.
There are already signs that temperatures well over 100 degrees could be common across the central United States by late next week, with scorching temperatures combining with high summer humidity to bring heat indices of 110 degrees in places.
Next week’s heat wave could be a long-lasting event over the central United States, potentially lasting into mid-August.
Scorching heat in the Pacific Northwest
Seattle weather records for July 29 since 1945. Number of times with measurable rain…4. The fewest number of rainy days of any calendar day. 29th precipitation total in 77 years…0.31″. Driest day of the year. Number of times with/high 90+…9. Most of any calendar day. # wawx pic.twitter. com/0d6yODDBQy
— NWS Seattle (@NWSSeattle) July 29, 2022
It’s been a hot week in the Pacific Northwest, and the heat isn’t letting up yet. Seattle hit 94 degrees on Tuesday, 91 on Wednesday and 91 on Thursday. Friday’s forecast high is 93 degrees and Saturday is expected to reach 92 degrees.
Five days is the longest streak on record at or above 90 degrees in Seattle. That happened in early July 2015. Seattle is currently expected to tie that record on Saturday, but there’s a decent chance Sunday will also hit 90. That would be a record for longest stretch of consecutive 90-degree days. The National Weather Service is forecasting a high of 88 degrees on Sunday.
The stretch may also be among the top 5 warmest five-day windows in Seattle. Based on current weather service forecasts, the five-day average high could be 92.6 degrees, tying Aug. 9-13, 1977, for fifth.
With the upper 90s here, here are 5 of the warmest 5-day stretches in Seattle (using average high temperatures).1. 97.2° June 25-29, 2021 95.8° July 26-30, 2009 95.0° August 7-11, 19814 92.8° July 20-24, 20065 92.6° August 9-13, 1977 Current Forecast 92.6° 26 -July 30, 2022 #wawx
— NWS Seattle (@NWSSeattle) July 29, 2022
“Extreme heat will greatly increase the risk of heat-related illness for much of the population, especially those who are heat-sensitive and those without effective cooling or adequate hydration,” the National Weather Service in Seattle wrote.
Portland is close to breaking its record for longest streak at or above 95 degrees – six days set in 1981 and 1941. So far it’s been four days – 99 degrees on Monday, 102 on Tuesday (daily record) and 96 on Wednesday and Thursday. Friday is expected to reach 99 degrees before reaching 101 on Saturday and 96 on Sunday.
The city of Portland could easily be hotter if a phenomenon called “down” occurs. This would mean the air would descend down the cascades before undergoing what is known as “adiabatic compression” as the air is heated and dried.
Instead, a “thermal low,” or band of low pressure caused by hot, rising air, stretches across the Cascades. This prevents drooping but also fends off the cooling sea breeze. The result? Portland is caught between a cooling influence and a warming effect, sitting right on the fence at about 100 degrees.
Further inland, temperatures are even hotter — Kennewick, Wash., could be near 111 degrees on Friday, Saturday and Sunday. By Monday, temperatures will return to the hundred-year mark.
In the northern parts of California’s San Joaquin Valley, highs will reach around 115 degrees in places. Heat warnings are also being issued for the Nevada Great Basin, the Columbia River Basin and Idaho.
On Thursday, many places in the interior of Northern California, Oregon and Washington saw record high temperatures of 100 to 115 degrees, including Medford, Oregon (111), Redding, California (115) and Yakima, Washington (109).
A heat dome or high pressure ridge feeds the heat – parked in the extreme northeast Pacific Ocean and adjacent western British Columbia. This brings hot and dry sinking air that crushes any cloud cover and allows additional heating. Highs will return closer to seasonal normals by early next week.
A new heat dome to dominate the Lower 48
Next on the weather map across the country is an even bigger heat wave that’s set to bring sweltering weather to much of the Lower 48. Signs point to a nearly coast-to-coast event with a stretched-out heat dome , which may exist for a week or More ▼.
The heat dome will deflect the jet stream toward Canada, allowing hot weather to accumulate in the south. The eastern half of the country will also face tropical humidity, with dew points near 70 degrees. This can result in heat indices in the 100 to 110 degree range.
The heat will start to increase significantly towards the middle of next week. High temperatures between 100 and 105 degrees will spread over Texas, Oklahoma, Kansas, Nebraska and Iowa on Wednesday; this may include Dallas, Fort Worth, Austin, San Antonio, Oklahoma City, Tulsa, Wichita, Kansas City, Omaha and Des Moines.
Upper 90s are more likely in the Upper Midwest, including Chicago, and throughout the Mississippi River Valley. On the East Coast, lows in the mid-90s could reach as far as the Mason-Dixon line.
If you’re hoping for some relief from the #heat, the GEFS and EPS models have just one word for you – fuhgettaboutit! A spinning wheel of #heatdomes spinning around the hemisphere forecast for the first half of August with the most impressive heat dome just over the central US. pic.twitter.com/Z8YFXcrgO9
— Judah Cohen (@judah47) July 28, 2022
By Thursday, the upper 90s could reach the Hudson River Valley to near Albany, and Boston could be looking at a high around 96. Bangor, Maine, could top out around 91 degrees — somewhat of a rarity this far north.
There are signs that the heat may peak in the Lower 48 between August 5 and 7 before consolidating over the Great Plains. Active weather, in the form of severe thunderstorms, may then spread across the Great Lakes, Northeast, and Mid-Atlantic as “ridge run” thunderstorms rise and pass along the northern periphery of the heat dome.
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