The stifling heat that settled over San Diego County this week will persist Thursday and last at least into early next week as the weather system causing the high temperatures is now stationary over the western United States, the National Weather Service said.
Temperatures could dip a few degrees Thursday, but with triple-digit heat in the forecast for much of the county and temperatures 10 degrees above average for late August, the slight cool-down will be almost imperceptible, the NWS said. And any slight drop in temperature won't last long — forecasters said Friday and Saturday will see the mercury jump back up several degrees as the heat wave is expected to last longer than previously thought.
The forecast has prompted the weather service to extend an excessive heat warning for the second time this week. Initially set to expire Wednesday, the warning's expiration was pushed back to Friday night and now to Saturday night. That warning covers most of the county except for the mountains and beaches, where a less serious heat advisory is in effect for the same time period.
Rain and thunderstorms could accompany the heat Thursday, mainly in the mountains and deserts, as monsoonal moisture moves into Southern California courtesy of a tropical storm of Mexico's west coast. Meteorologists put the chance of rain Thursday at 20 percent in San Diego County's mountains and deserts.
On Wednesday, Ramona topped out at 105 degrees to tie its Aug. 30 record high. Other notable high temperatures included Valley Center hitting 109, Escondido topping out at 101, Alpine reaching 103 and Campo touching 107. In the desert, Borrego Springs reached 114 and Ocotillo Wells was the hottest spot in the county at 117.
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High temperatures Thursday will be 81 to 86 degrees at the beaches, 92 to 97 inland, 95 to 100 in the western valleys, 100 to 105 near the foothills, 94 to 100 in the mountains, and 108 to 113 in the deserts.
The NWS reminded residents that during an excessive heat warning, "persons working outdoors or those without access to adequate air conditioning will be more likely to experience heat-related illness, such as heat exhaustion. Some heat related illnesses are serious enough to require hospitalization and could become fatal if left untreated."
The weather service reminded residents to never leave children, seniors or pets unattended in cars; drink more water than usual and avoid alcohol, sugar and caffeine; wear light-colored clothing and a wide-brimmed hat outdoors to keep the head and body cooler; and take frequent rest breaks in shaded or air-conditioned environments.
