Record-Breaking Heat Broils Much of Western U.S.

Millions of people across the Western United States were broiling under record-breaking heat on Saturday, with little relief in sight over the coming days, according to forecasters.

From Oregon to California to the deserts of Arizona, several cities have seen stifling temperatures in recent days. Jacob Asherman, a forecaster for the National Weather Service’s Weather Prediction Center, said the blistering temperatures were being fueled by a ridge of high-pressure air that had parked over much of the West, preventing hot air near the surface from rising higher in the atmosphere.

While many of these cities — like Las Vegas, where temperatures were forecast to reach 117 degrees over the weekend — expect triple-digit temperatures every summer, some residents in other regions were caught off guard by what is predicted to be a long stretch of sizzling days.

In Portland, Ore., temperatures were forecast to hover around 100 degrees for five straight days starting Friday, conditions that once would have been considered unusual for a region where summers were so mild that people rarely needed air-conditioners. The sweltering temperatures prompted Gov. Tina Kotek to declare a statewide heat emergency, warning that the extreme heat represented a “new normal” of a changing climate.

“Both the record-breaking temperatures and the duration of heat present a clear and present danger, particularly for children, elders, people with disabilities and people who work outside,” Ms. Kotek said in a statement.