An Extreme Heat Warning will take effect Friday morning for parts of San Diego County, where forecasters expect highs in the 90s near the coast and temperatures above 100 in inland valleys. The County said Thursday that the heat could persist into next week, while Santa Ana winds and dry air create a second hazard: conditions that can carry a small ignition quickly across dry vegetation.
The warning changes the problem after sunset as well as during the afternoon. Warm overnight lows reduce the hours when buildings and bodies can cool, allowing strain to accumulate across several days. Older adults, young children, pregnant people, outdoor workers and people with chronic medical conditions face greater risk of heat exhaustion or heatstroke. Dizziness, nausea, confusion, heavy sweating, headache and fainting require prompt attention.
Thirty-three County branch libraries and community centers are serving as Cool Zones, giving residents access to air-conditioned space. The County advises people to drink water, avoid alcohol and sugary drinks, wear loose clothing and move strenuous activity away from the hottest hours. Fans alone are not a safe cooling strategy when indoor temperatures exceed 90 degrees, and no child, older adult or animal should be left in a parked vehicle.
The dry wind also puts the electric system into the forecast. San Diego Gas & Electric is monitoring whether it must use Public Safety Power Shutoffs through Oct. 5 to reduce the chance that energized equipment starts a wildfire. A shutoff is preventive, not proof of a fire, and the utility had not announced a regionwide outage. Its PSPS dashboard is the place for address-level updates as the weather changes.
Outage preparation matters most before a circuit is de-energized. The County recommends charging phones, flashlights and medical devices, cooling homes early, keeping water available and making a communication plan with relatives and neighbors. People who depend on powered medical equipment have less room to improvise. They need to know where they can relocate and how long batteries will sustain essential devices.
Heat, wind and electricity meet differently across the county's terrain. Inland valleys may record the highest temperatures, while foothill and backcountry communities can face stronger wind and a larger wildfire exposure. Near the Tijuana River Valley, heat can intensify hydrogen sulfide odors. County guidance there is to limit outdoor activity, close windows and set air conditioning to recirculate when odors are present.
Residents can register phone numbers at AlertSanDiego.org for emergency notices. Fire prevention during a Red Flag period also depends on ordinary choices: secure trailer chains so they do not spark, dispose of cigarettes safely and postpone work that can ignite vegetation. Those precautions do not eliminate the regional risk, but they reduce avoidable ignition sources when fuels are receptive to fire.
The warning covers a sequence rather than a single hot afternoon. County emergency teams said they are tracking the weather, coordinating with public-safety partners and contacting vulnerable clients in areas that may be affected. The practical test will be whether cooling sites, outage notices and transportation options reach people before indoor temperatures become unsafe—not after the heat and wind have already narrowed their choices.