Why is there a heatwave in the Southwestern U.S.?
Beginning on May 8, 2026, a heatwave will affect a significant portion the southwestern United States, including Arizona, Nevada, and Southern California (1)(2).
This heat event is driven by a strong high-pressure system, with temperatures expected to climb 20 to 30 degrees Fahrenheit in just a few days. Phoenix, Las Vegas, and Fresno are among the cities that could experience their first 100-degree day of the year, with some daily temperature records potentially being challenged.
A heatwave in May is unusual for the time of year, though not as extreme as the heatwave that occurred in March.
Which cities or areas are affected by the heatwave?
Several cities in Arizona, California, and Nevada will experience extreme heat over the weekend, including:
- Fresno, California
- Indio, California
- Lake Havasu City, Arizona
- Las Vegas, Nevada
- Phoenix, Arizona
- Yuma, Arizona
How long will the heatwave last?
The heatwave is expected to begin May 8, 2026, and last through at least Monday night, May 11, 2026, with some areas experiencing elevated temperatures into Tuesday evening, May 12, 2026.
Are there any alerts in place?
As of May 8, Extreme Heat Watches have been issued for multiple areas, including parts of Imperial County, the Salton Sea region, Coachella Valley, San Diego County deserts, and the San Gorgonio Pass near Banning (3). An extreme heat watch is also in place in Phoenix (4).
Authorities advise residents to take precautions. These include staying in air-conditioned spaces, avoiding direct sun exposure, drinking plenty of fluids, and checking on vulnerable individuals such as older adults, young children, and those with preexisting health conditions.
Outdoor workers are urged to reschedule strenuous activities to early morning or evening hours and take frequent breaks in shaded or cooled environments. Heat stroke is a serious risk, and anyone showing symptoms should receive immediate medical attention.
