Record-Breaking Heat Dome Engulfs the Western United States

A powerful high-pressure system, described as a “heat dome,” moved from the Southern United States into the West on Friday, trapping hot air near the surface. The National Weather Service issued extreme-heat warnings for Southern California, Arizona, Nevada, Utah and parts of the Southwest. Forecasts called for afternoon highs of 103 °F in Sacramento, 105 °F in Salt Lake City, 115 °F in Las Vegas and 117 °F in Palm Springs, with inland Bay-Area locations expected to reach the triple-digit range. Death Valley was projected to hit 126 °F, the highest temperature of the wave.

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Heat domes act like lids on a pot, preventing warm air from rising. Scientists note that a warming climate is making such domes stronger and slower-moving, increasing the likelihood of record-breaking heat events. This wave follows a summer of simultaneous heat extremes across the United States and Europe.

CNN

The heat wave placed roughly 40 million people under heat alerts, with about 12 million on a Level 4 “extreme” risk and another 12 million on Level 3 “major” risk, according to the National Weather Service. By August 4, an estimated 10 % of the contiguous United States is expected to record its hottest day of the year so far. Temperatures above 100 °F were forecast for much of California, while Phoenix, Tucson and Las Vegas were expected to exceed 110 °F. Overnight lows were projected to remain about 10 °F above normal, limiting nighttime relief.

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Heat is the deadliest form of extreme weather in the U.S., with the National Weather Service reporting higher annual fatalities than tornadoes, hurricanes or lightning combined. In Maricopa County, data shows 40 confirmed heat-related deaths this year. The Los Angeles County Fire Department reported nearly 2,000 ocean rescues last week as beachgoers sought relief. The sustained heat is drying soils and vegetation, heightening wildfire risk across the Colorado River Basin. Simultaneously, evaporation is accelerating the decline of Lake Mead and Lake Powell, two major reservoirs that supply water to tens of millions of people.

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The National Weather Service warned that the extreme-heat conditions increase the risk of heat-related illnesses and urged residents to stay hydrated, seek shade and use cooling centers where available. Local authorities, including the Los Angeles County Fire Department, emphasized beach safety and posted rescue statistics on social media. The heat dome is expected to linger, with additional hot weather predicted to begin on August 6.

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