A heatwave that smashed all-time high temperature records in western Canada and the US Northwest has left a rising death toll in its wake as officials brace for more sizzling weather and the threat of wildfires.

The worst of the heat had passed by Wednesday, but the state of Oregon reported 63 deaths linked to the heatwave. Multnomah County, which includes Portland, reported 45 of those deaths since Friday, with the county Medical Examiner citing hyperthermia as the preliminary cause.

By comparison all of Oregon had only 12 deaths from hyperthermia from 2017 to 2019, the statement said. Across the state, hospitals reported a surge of hundreds...