Heat dome to bring dangerous 115F highs to 45 million in south-west

Los Angeles opens cooling centers as wildfires rage across region

The National Weather Service warned on Tuesday that a heat dome building across the US south-west will push more than 45 million people into dangerous late-summer temperatures through the end of August and into early September, with daytime highs forecast at 110 to 115F (43 to 46C).

“A strong upper-level ridge will remain anchored across the south-west into south-central US into late week,” the NWS said in its short-range forecast discussion. The agency said the ridge would maintain “abnormal hazardous heat across the region,” with daytime highs of 100 to 110F across the Southern Plains and up to 115F in parts of the south-west.

The NWS classified the conditions as Extreme HeatRisk, a level it considers dangerous to people who lack proper hydration or the capacity to cool down. A heat dome forms when strong high pressure traps hot air over a region, preventing cooler air from moving in and allowing ground-level temperatures to climb and remain elevated.

With overnight temperatures offering little relief, the agency warned that heat-related illness could increase, especially among people without adequate cooling. The NWS urged residents to limit outdoor activity, stay hydrated, wear loose and lightweight clothing, and check on older adults and children, whose bodies regulate temperature less effectively.

The agency also warned against leaving anyone alone in a closed car. The advocacy organization No Heat Stroke reported that 34 children died in hot cars in the United States in 2025, with cases extending into December in parts of the south.

Wildfires are burning in parts of the region as the heat builds, and the NWS is forecasting monsoonal moisture across the south-west, the US Rocky Mountains and the plains, bringing heavy scattered showers and thunderstorms. Continued humidity, the agency said, compounds the heat risk.

Cities have begun opening cooling centers. Los Angeles announced access to facilities for residents seeking relief, and other affected cities have made similar arrangements.

Researchers have linked the pattern of intense summer heat domes to climate change. Writing in the Proceedings of the National Academy of Sciences, scientists said that “climate change is increasing the frequency and severity of summer extreme weather events in the mid-latitudes of the Northern Hemisphere, from record-shattering heatwaves to heavy precipitation and flooding, to prolonged droughts and more extensive wildfires, as well as compounding effects due to interactions between extreme events.”