An extreme heat warning covers Del Mar, Solana Beach and Rancho Santa Fe through Wednesday evening. The National Weather Service expects coastal temperatures to reach the mid-80s to 90s, well above the upper-70s typical for early September.
San Diego County announced the warning Tuesday, Sept. 8, on X, noting that coasts and valleys face extreme heat while the mountains are under a heat advisory. The NWS issued the warning at 3:44 a.m. Tuesday, and it runs through 8 p.m. Wednesday, Sept. 9, according to the OC Register. The NWS classified the threat as "Major to Extreme HeatRisk" through Wednesday.
It will not cool down much at night. The NWS forecast calls for overnight lows in the lower to mid-70s across coastal and valley areas, limiting the body's ability to recover from daytime heat.
Residual moisture from Tropical Storm Marie, which passed through Southern California over Labor Day weekend, is adding humidity that NWS forecasters said will worsen the heat's impact, according to Patch. Inland valleys could see highs near 108 degrees, and desert areas could reach 111, NBC 7 San Diego reported.
Once the warning expires Wednesday evening, a heat advisory takes its place through 8 p.m. Thursday, Sept. 10. Some cooling is expected near the coast Thursday, spreading inland Friday.
Who is at risk
Infants, young children, older adults and people with chronic medical conditions face the highest risk of heat illness, according to San Diego County's health department. The NWS warned that car interiors can reach lethal temperatures within minutes and urged residents to never leave pets or children unattended in vehicles, NBC 7 San Diego reported.
Cooling resources
Dozens of locations across San Diego County operate as Cool Zones, free air-conditioned spaces open to anyone. A downloadable list of active sites is available on the county's Cool Zones page. Residents can call 1-800-339-4661 Monday through Friday, 8 a.m. to 5 p.m., or email [email protected].
The county's heat safety tips page advises residents to drink plenty of water, stay in air-conditioned rooms, stay out of the sun and check on friends and neighbors at high risk for heat-related illness.
The extreme heat warning covers all San Diego County coastal areas and valleys. Del Mar, Solana Beach and Rancho Santa Fe fall within those zones, though the NWS warning does not name individual communities.
