Published July 8, 2025 – 10:30 a.m. ET
From Tuesday, July 9, an intense heat wave will grip much of the western United States, with California at the epicenter of the event. According to the National Weather Service (NWS) and NOAA, a heat dome is expected to settle over the region, pushing temperatures well above 100°F (38°C) across large portions of the state. Authorities have already issued heat advisories due to the threat to public health and infrastructure.
Most affected areas in California
Some of the most impacted counties will experience dangerously high heat levels, reaching the red or magenta HeatRisk categories, the highest alert levels issued by NOAA.
Fresno, Kern, and Tulare counties will see scorching temperatures between 105°F and 110°F (40°C to 43°C), under intense solar exposure and very low humidity.
Riverside and Imperial counties, particularly in desert zones, are expected to peak at over 110°F (43°C), putting these areas at extreme risk of heat-related illness.
The Sacramento and San Joaquín Valleys will face several consecutive days of extreme heat, with elevated overnight lows that may prevent sufficient cooling during the night.
In northern California, Shasta and Tehama counties will be under severe risk, as hot, dry conditions elevate the danger of both heat exhaustion and wildfire outbreaks.
Coastal areas with milder conditions
The marine layer will help moderate temperatures along the coast. Cities like San Francisco, San Mateo, and Alameda will remain relatively cool, with daytime highs between 60°F and 75°F (15°C to 24°C).
In Marin County and the Sonoma coast, highs will stay below 80°F (27°C).
Even in Los Angeles, where coastal areas will benefit from the cooling influence of the Pacific, inland neighborhoods are forecast to reach above 90°F (32°C).
Other western states under heat threat
The heat dome will not remain confined to California. Several other western U.S. states are also expected to sizzle under the expanding wave.
In Arizona, cities like Phoenix and Yuma could soar to 115°F (46°C), with extreme heat warnings already in place, especially for urban and desert regions.
Nevada, and particularly Las Vegas, will face daytime highs ranging between 110°F and 112°F (43°C to 44°C), with heat alerts likely to continue through the weekend.
Interior areas of Oregon, Idaho, and Washington are expected to exceed 100°F (38°C), particularly across agricultural zones and valleys.
Utah and New Mexico will see maximums between 103°F and 108°F (39°C to 42°C), with heat risks highest in rural regions and outdoor recreation areas.
