Temperatures soar above 110° in Pacific Northwest, possible ‘1 in 1,000-year’ event

What is behind the unusual summer pattern?

Meteorologist Sarah Spivey takes some time to talk through a record shattering heat wave in the Pacific Northwest, and the "heat dome" that's making it happen.

It’s the kind of temperature map that’ll make you do a double-take. Usually, it’s the nation’s mid-section baking under summer heat this time of year. Instead, the United States’ two coasts are feeling the extreme heat.

The Pacific Northwest, in particular, is seeing the most intense readings, where temperatures are some 30 degrees above average. On Sunday, many spots soared above 100°, while some locations topped 110°. The National Weather Service called the event “historic, dangerous, prolonged and unprecedented, “considering a substantial part of the population does not have air conditioning. Some scientists are calling it a 1 in 1,000-year event.

Portland, Oregon112°
Eugene, Oregon111°
Olympia, Washington105°
Seattle, Washington104°
High temperatures Sunday, June 27, 2021 (Copyright 2021 by KSAT - All rights reserved.)

International Heat Wave

The extreme heat doesn’t stop at the border, as Canada is also seeing record-breaking high temperatures. On Sunday, Lytton, British Columbia, recorded Canada’s all-time highest temperature, topping out at 116°. To put that into perspective, San Antonio’s all-time high is 111°, set in September of 2000. For the first time in history, heat warnings have been issued all the way up the Arctic Circle.

Monday June 28, 2021 excessive heat warnings stretched through Canada to the Arctic Circle. (Copyright 2021 by KSAT - All rights reserved.)

Why so hot?

Behind the unprecedented heat wave is a heat dome centered over the United States and Canadian border. Its intensity is stronger than any high pressure seen in this region in recorded history. Climate change is likely playing a role in the extreme peaks and valleys seen in the weather pattern over the last few years, including in this case. Heat domes form under high pressure, where sinking air creates warmer-than-normal temperatures. The stronger the high pressure, the hotter the temperatures.

Many times, powerful ‘heat highs’ will sit over Texas, creating summer droughts and triple-digit temperatures. In this odd pattern, the heat high has reformed over the nation’s two coasts, leaving Texas, and the middle of the country, in a cooler, more unsettled pattern. Highs in San Antonio over the next few days are forecast to be in the 80s.

The heat in the Pacific Northwest is forecast to subside by the middle part of the week.

About the Authors:

Justin Horne is a meteorologist and reporter for KSAT 12 News. When severe weather rolls through, Justin will hop in the KSAT 12 Storm Chaser to safely bring you the latest weather conditions from across South Texas. On top of delivering an accurate forecast, Justin often reports on one of his favorite topics: Texas history.

Sarah Spivey is a San Antonio native who grew up watching KSAT. She has been a proud member of the KSAT Weather Authority Team since 2017. Sarah is a Clark High School and Texas A&M University graduate. She previously worked at KTEN News. When Sarah is not busy forecasting, she enjoys hanging out with her husband and cat, and playing music.