Canadian authorities said the historic heatwave gripping the Pacific Northwest caused “unprecedented casualties,” as a fourth day of historic heat spread searing temperatures inland even as some relief arrived for coastal areas. At least 233 people in British Columbia have died since Friday, twice the usual number reported to the coroner’s office over a four-day period. The deaths of five people in King and Snohomish Counties, in Washington, and a farm worker in St. Paul, Oregon, were blamed on the heat. Heat exposure is suspected in another four deaths in Puget Sound City, Wash., and the deaths of two people without homes in Bend, Oregon, but has not been definitively determined. More than 1,100 people in Washington and Oregon sought treatment at hospitals for heat-related illness. Heat waves are especially deadly for those who are already vulnerable, with Ingenious and Black communities suffering the highest rate of heat-related deaths.

Meanwhile, tens of thousands of residents in the Pacific Northwest were without power this week. Avista Utilities, which serves eastern Washington, Idaho and Oregon, instituted rolling blackouts for the first time in its history Tuesday as temperatures in Spokane, Wash., climbed to 109°F and nearly 10,000 customers there lost power Monday. “The electric system experienced a new peak demand, and the strain of the high temperatures impacted the system in a way that required us to proactively turn off power for some customers,” Avista President Dennis Vermillion said. The company pointed to distribution, not electricity supply, for the outages. (CNNAPThe OregonianBloomberg $, AxiosAl JazeeraBuzzfeed)