Record-breaking heatwave to hit Pacific Northwest and West Coast.

A heat wave is expected to hit the Pacific Northwest and southwest Canada, with temperatures reaching 20 to 35 degrees above normal. Locations west of the Cascade Range, including Portland and Seattle, have been placed under a heat advisory. The unusually toasty temperatures will be caused by a powerful zone of high pressure, also called a heat dome. The heat wave will also increase the risk of wildfires in Alberta, Saskatchewan, and surrounding areas. Temperature records are expected to be broken in several locations, and snowmelt is likely to accelerate in the Sierra Nevada of California.