Extreme Heat Watches issued for California and Arizona as anomalous heat intensifies across parts of the Southwest
Extreme Heat Watches have been issued for parts of California and Arizona as an anomalous and unusually prolonged heat event intensifies across the Southwest United States. Watches begin Monday, March 16, 2026, in parts of Southern California, then expand into parts of Arizona and southeast California later in the week, with some desert areas forecast to reach up to 43°C (109°F) and temperatures in some locations rising 11–17°C (20–30°F) above normal for mid-March.
GFS 2m Temperature Anomaly for March 17, 2026. Image credit: Tropical Tidbits
Extreme Heat Watches have been issued by the National Weather Service (NWS) across the southwestern United States as an unusually early and prolonged heat wave is forecast to affect parts of California and Arizona during the week of March 16–22.
Temperatures in the affected region are forecast to reach around 35–43°C (95–109°F), with some areas expected to run 11–17°C (20–30°F) above normal for mid-March.
Currently, an upper ridge will maintain a prolonged warm-up for parts of the West and Southwest this weekend. Daily high temperatures on March 14 are forecast to range 15–26°C (60–70°F) across the Great Basin, 21–32°C (70–80°F) across northern California, and 32–37°C (90–100°F) across southern California and the Desert Southwest.
Some daily record-tying or record-breaking highs will be possible for Southern California and the Desert Southwest on March 14, before a more anomalous and widespread phase of the heat event develops next week.
“These temperatures will serve as a baseline for even more anomalous, more widespread record-breaking heat expected into next week,” the NWS Weather Prediction Center said.
California
The NWS Los Angeles/Oxnard office has issued an Extreme Heat Watch for a large portion of southwest California from Monday morning, March 16, through Friday evening, March 20. The watch includes coastal and inland areas of San Luis Obispo, Santa Barbara, Ventura, and Los Angeles counties, including the Santa Clarita Valley, San Fernando Valley, San Gabriel Valley, Malibu Coast, and portions of the Channel Islands. Forecast conditions indicate a historic and prolonged March heat episode, with temperatures potentially reaching around 38°C (100°F).
The NWS San Diego office has also issued an Extreme Heat Watch for coastal and inland areas of Orange County, San Diego County, and the Inland Empire, including valleys of San Bernardino and Riverside counties. The watch remains in effect from Monday morning, March 16, through Friday evening, March 20. Temperatures are forecast to reach 29–32°C (85–90°F) near the coast and up to 40°C (105°F) inland, with highs in some areas expected to run approximately 11–17°C (20–30°F) above normal for this time of year.
An additional Extreme Heat Watch has been issued for the Santa Ana Mountains and foothills in Southern California for the same period. Temperatures in these areas may reach up to 34°C (93°F), and forecasters note that the early-season timing and prolonged nature of the event could increase the risk of heat-related illnesses, particularly for vulnerable populations and those without access to cooling systems.
Arizona
The NWS Tucson office has issued an Extreme Heat Watch for several lower-elevation valleys, including the Upper Santa Cruz River Valley, Upper San Pedro River Valley, Upper Gila River Valley, and eastern Cochise County below 1 524 m (5 000 feet). The watch is in effect from Thursday morning, March 19, through Sunday, March 22. Forecast temperatures in these regions are expected to reach 35–38°C (95–100°F), with the hottest conditions currently forecast for March 20 and 21.
Another Extreme Heat Watch covers the Tucson metropolitan area, western Pima County, the Tohono O’odham Nation, and parts of Pinal County, with forecast high temperatures potentially reaching 38–42°C (100–108°F) during the peak of the event.
The NWS Phoenix office has issued an Extreme Heat Watch affecting parts of southwest Arizona and southeast California, including the Parker Valley, Palo Verde Valley, Imperial Valley, Chuckwalla Mountains, and the Salton Sea region.
In southeast California and parts of the lower Colorado River Valley, the watch begins Wednesday morning, March 18, before expanding into more of southern Arizona on Thursday, March 19. Afternoon temperatures are forecast to reach approximately 39–43°C (103–109°F).
Authorities warn that extreme heat events significantly increase the risk of heat exhaustion and heat stroke, particularly for young children, older adults, outdoor workers, and those without air conditioning. Officials also warn that temperatures inside parked vehicles can reach lethal levels within minutes.
References:
1 Extreme Heat Watch – NWS – March 14, 2026
2 Short Range Forecast Discussion – NWS – March 14, 2026
I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.
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