Extreme Heat Watch: Historic March Heat Wave Grips Los Angeles, San Diego, and Southern California This Week
A once-in-a-generation extreme heat watch is now in effect across Southern California, and today marks the beginning of the most dangerous stretch. Extreme Heat Watches activated Monday morning, March 16, across a massive swath of southwest California and Arizona, with temperatures forecast to reach 35–43°C (95–109°F) — running 11–17°C (20–30°F) above normal for mid-March. Millions of residents from Los Angeles to San Diego are urged to take immediate precautions as the worst days of the heat event are still ahead.
Extreme Heat Watch in Effect Now — Los Angeles, San Diego, Orange County
The National Weather Service has issued the most serious heat alerts available across an enormous portion of Southern California this week.
The NWS Los Angeles and Oxnard office 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.
The watch is also valid across Orange County Coast, Orange County, San Diego County Coastal Areas, San Bernardino and Riverside County Valleys, and San Diego County Inland Valleys through Friday, March 20, at 8 p.m. PT. Dangerously hot conditions with temperatures of 85 to 90 degrees near the coast and up to 105 degrees inland are expected.
Record-Breaking Temperatures Expected Through Friday
The NWS Los Angeles office described the event as a "historic, long and record breaking March heatwave" with dangerously hot conditions up to 100 degrees possible within the Extreme Heat Watch area. Temperatures are running 15 to 25 degrees above normal through Friday, with a brief Saturday cooling followed by a stronger high-pressure ridge next week potentially triggering excessive heat warnings from Tuesday through Thursday.
NWS meteorologist Sebastian Westerink confirmed this is very anomalous heat for the month of March, noting that temperatures in the upper 90s or 100s are typically not seen until June. The average high temperature for the area during this time of year is 73 degrees.
Desert Heat Could Hit 105–110 Degrees — Extreme Conditions for Coachella and Palm Springs
The most extreme temperatures of the entire event will be felt in the desert communities of the Inland Empire and San Diego County deserts.
The Coachella Valley, San Gorgonio Pass near Banning, and San Diego County Deserts are under an Extreme Heat Watch valid from Thursday morning through Friday evening, March 20, at 8 p.m. PT. Dangerously hot conditions with temperatures of 105 to 110 degrees are possible, running 20 to 30 degrees above normal for this time of year. Record-breaking heat is likely.
In the mountain regions, including Big Bear Lake, Running Springs, Idyllwild, Lake Arrowhead, Julian, and Pine Valley, temperatures of 85 to 95 degrees are possible below 5,500 feet elevation — also 20 to 30 degrees above normal for mid-March.
Extreme Heat Warning Could Be Upgraded This Week
A brief Saturday cooling will be followed by a stronger high-pressure ridge next week, potentially triggering excessive heat warnings from Tuesday through Thursday. Officials are warning of high risks for heat illness, especially for workers and residents in coastal areas lacking air conditioning.
An Extreme Heat Watch is issued when weather conditions are favorable for dangerously hot temperatures in the coming days but exact timing or magnitude may still change. If forecasters' confidence increases that dangerous heat will occur, the watch could be upgraded to an Extreme Heat Warning.
How Each Region Compares This Week
| Region | Expected High | Degrees Above Normal |
|---|---|---|
| Downtown Los Angeles | Up to 100°F | +20 to +25°F |
| San Fernando Valley | 95–100°F | +20 to +27°F |
| San Diego (Inland) | 93–98°F | +20 to +25°F |
| San Diego (Coast) | 88–92°F | +15 to +19°F |
| Coachella Valley | 105–110°F | +20 to +30°F |
| Orange County (Inland) | 95–105°F | +20 to +30°F |
Worker Safety Protocols Activated Across California
Cal/OSHA and labor unions including the International Union of Bricklayers and Allied Craftworkers have activated safety protocols including mandatory shade, electrolyte packets, and frequent breaks specifically to protect workers who are not yet acclimatized to high heat.
The extreme heat poses a serious risk to vulnerable populations including young children, older adults, and those without access to air conditioning or who must work outdoors. California officials say this early-season heat event is highly unusual and poses a serious threat to public health.
Extreme Heat Watch Safety — What to Do Right Now
Never leave children or pets in a locked vehicle, as interior temperatures can become fatal within minutes. Schedule strenuous outdoor tasks for the early morning or late evening. Visit elderly relatives or neighbors who may not have adequate cooling at home.
Cooling center locations are available for residents in Los Angeles County at ready.lacounty.gov/heat, in Orange County at ocgov.com/cooling-centers, and in Riverside and San Bernardino Counties at capriverside.org/cool-centers. The Extreme Heat Watch remains in effect through Friday, March 20 — monitor the National Weather Service and local news for any upgrades to an Extreme Heat Warning as conditions evolve throughout the week.
