A National Weather Service Extreme Heat Warning covering San Diego County is in effect through 8 p.m. Thursday, bringing sustained hot and humid conditions and elevated overnight temperatures that increase the risk of heat-related illnesses for residents.
The warning applies to the San Diego County inland valleys and mountains, where daytime highs are expected to reach the upper 90s to 100 degrees in the valleys and upper 80s to 90s in the mountains. The advisory also covers adjacent inland areas of Orange, Riverside and San Bernardino counties.
What residents should expect
Forecasters with NWS San Diego said hot, humid conditions will keep overnight lows in the upper 60s to lower 70s, reducing nighttime relief from daytime heat. The agency warned that people who spend long periods outdoors face a higher risk of heat-related illnesses.
"Heat related illnesses increase significantly during extreme heat events. Those spending long periods outdoors will be at greater risk for heat health impacts."
Officials urged residents to take precautions: stay in air-conditioned spaces, drink plenty of fluids, avoid strenuous activity outdoors during the hottest hours, and check on relatives and neighbors who may be vulnerable.
- Expect daytime highs: low 90s to 100+ in inland valleys
- Elevated overnight temps: upper 60s to lower 70s
- High risk groups: elders, young children, people with chronic illness, outdoor workers
Temperatures by area
| Area | Expected highs |
|---|---|
| San Diego County Valleys | upper 90s to 100 |
| San Diego County Mountains | upper 80s to 90 |
| Inland Empire (Riverside/San Bernardino valleys) | 100 to 103 |
| Inland Orange County | low 90s |
Daytime outdoor recreation is discouraged, the NWS said, and residents should plan accordingly for work, travel and school pickups. Cooling centers and shaded public spaces can offer relief; check local city and county websites for locations and hours.
The warning also covers other Southern California inland regions, including the San Gorgonio Pass near Banning and the Santa Ana Mountains and Foothills. With limited overnight cooling, heat stress can accumulate across consecutive hot nights and days, increasing risk for wildfire starts and health complications.
Local authorities recommend that people who must be outdoors take frequent breaks, drink water even if not thirsty, wear light clothing, and avoid alcohol or heavy meals that can worsen dehydration.
Monitor updates from NWS San Diego and local public health agencies for changes in the forecast and information about heat-relief resources.
