A stifling "heat dome" is parked over the Pacific Northwest, bringing unprecedented heat to at least 25 million in the United States, and more in Canada. Temperatures are forecast to hit an apex Sunday and Monday in many areas.
Why it matters: Extreme heat threatens lives, ranking as the nation's top weather-related killer annually. In addition, extreme heat events such as this one are a clear manifestation of human-caused climate change, with numerous studies linking such events to the long-term increase in global average temperatures.
- Making the health threat more acute, this heat wave is a prolonged event with little overnight relief, as temperatures Sunday morning were near 80°F in Seattle and Portland.
- The heat is also affecting areas where less than half of residents have air conditioning, including Seattle.
Driving the news: A highly unusual weather pattern is in place over the Pacific Northwest, with a record-strong high-pressure area aloft — known as a "heat dome" — sitting over Washington State and British Columbia, weakening little through Monday and sliding only slowly eastward.
- This heat dome is yielding temperature departures from average of between 25°F to 45°F and above across multiple states and British Columbia.
- This heat, combined with a worsening drought, is raising the risk of wildfires across multiple Western states.
- It is also causing power demand to spike at a time when hydropower resources are lower than usual due to the drought conditions.
By the numbers: All of Oregon and Washington, plus portions of California, Idaho, Montana and Nevada, are under excessive heat watches and warnings. ...
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