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How Significant Was Last Month’s Heatwave?

Last Modified Date: February 17, 2023

This summer’s extreme heatwave in the Pacific Northwest of the United States and Canada's western provinces produced some eye-popping temperatures in areas where air conditioners are rarely used. For example, temperatures reached an all-time record of 121.3 degrees Fahrenheit (49.6 degrees Celsius) in Canada. In Oregon, the cables that provide power for Portland’s streetcar system melted in the 112 °F (44 °C) swelter.

All told, June 2021 was the hottest June ever recorded in North America. Several cities in the United States and Canada suffered through temperature increases of more than 7 °F (4 °C) above previous records.

Hot, hot, hot:

This year’s heatwave resulted from a phenomenon called an omega block, which is a dome of hot air trapped in place by atmospheric currents.

On June 28, Seattle recorded its hottest day ever, a miserable 108 °F (42 °C) That's about 34 degrees (Fahrenheit) above the normal highs the city experiences at that time of year.

In British Columbia, 579 deaths were attributed to the oppressive heat. In the U.S., the heatwave was blamed for 116 deaths in Oregon, and 78 deaths in Washington state.