WeatherWeather Science


After a historic heatwave, Pacific Northwest heat dome is slowly eroding

Pacific NW Record Heat
Omega Block graphic
Posted at 5:20 PM, Jun 29, 2021

All-time record heat is crippling the Pacific Northwest, an area where most residents don't have air conditioning.

Places like Seattle and Portland have spent the past few afternoons in the triple digits, setting all-time heat records along the way.

Pacific NW Record Heat
New Pacific Northwest All-Time Records

The hottest in Oregon, The Dalles, saw an extremely toasty high on Monday of 118 degrees.

It's now the second hottest temperature reading ever for the Beaver State, a record that dates back to 1898, when Pendleton topped out at 119 degrees.

Not to be outdone, Oregon's capital city Salem reached 117 degrees on Monday.

The Portland Airport came in at 116 degrees, and Vancouver, Washington, a suburb of Portland soared to 115.

In the Puget Sound Region, Olympia and the Seattle-Tacoma Airport also set new all-time records, warming to 110 and 108 respectively.

Omega Block graphic
Omega Block Pattern explainer graphic

A weather pattern known as an Omega block is responsible for those baking hot temperatures

This occurs when an amplified high pressure system develops between two cut-off areas of low pressure. A pattern that often remains stagnant for days (or weeks) at a time, and may produce different types of weather extremes.

Some experts are calling this a one-in-a-thousand year event.

Finally today, it's beginning to cool down for the coast and coastal valleys thanks to a return of the onshore flow. Farther inland on the east side of the Cascades, the heat remains.

Beginning Wednesday, Seattle will fall back into the 80s, and although above average, it's a significant change for the area.

Portland will be cooler for the rest of the week too, with highs in the upper 80s and lower 90s through Friday.

If you're wondering if the Pacific NW heat is coming to Southern Colorado next, the answer is no. The heat ridge will pass well to our north and not affect us through the upcoming holiday weekend.