Last updated October 15, 2021
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Northwest US Heat Wave August 2017

United States

During the first three days of August 2017, some locations in the Pacific Northwest approached their hottest temperatures ever recorded.[1] Much of the Pacific Northwest sweltered in a prolonged heat wave beginning in late July. The heat set some all-time heat wave longevity records in a few locations.[2] The heat was caused by a high pressure system in the atmosphere, which helped keep skies free from clouds and allowed the sun’s energy to heat the surface.

Record breaking heat waves are a classic signal of climate change. The trend in global warming has contributed to the severity and probability of 82 percent of record-hot days globally over the 1961-2010 period.[3]

The kind of stalled weather pattern that intensified the northwestern heat wave is the sort of pattern expected due to climate change.[4]

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Smoke from wildfires in BC and extreme heat create a haze over Seattle in early August 2017. Photo: InnerEye Photography

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