A red flag fire danger warning outside a fire station in Valley Center. Courtesy OnScene.TV

San Diego County will be under a red-flag warning for extreme fire danger Thursday, as gusty Santa Ana winds and low humidity combined to heighten the risk of wildfires and nearly 75,000 local utility customers had their electricity shut off as a precaution.

Humidity levels dipping below 10%, sustained 30-plus-mph winds and gusts of 60 mph or higher will create “extremely critical” combustion hazards Thursday in local mountain communities into the early afternoon, according to the National Weather Service. Affected highland areas include those east of Chula Vista, El Cajon, Escondido and Fallbrook.

The warning took effect at 6 p.m. Wednesday and will continue until 10 p.m. Saturday for local inland valley and highland areas. The most intensive critical fire-weather conditions were expected to last through Friday morning, meteorologists advised.

As of 7:15 a.m. Thursday, peak wind gusts had reached 95 mph on Big Black Mountain in Mesa Grande, followed by 93 mph at Sill Hill, 84 mph in Hellhole Canyon and 77 mph in Boulder Creek, Horse Launch and Hauser Mountain, according to the weather service.

Due to the wildfire warning, San Diego Gas & Electric on Tuesday notified about 88,700 of its customers in inland communities that they could be subject to public-safety power shutoffs from Wednesday night into the weekend, and potentially through Monday. As of Thursday morning, 73,348 customers had their power shut off, with another 21,806 under consideration for shutoffs, according to the SDG&E web site.

Because of the precautionary power shutoffs, schools in the Alpine Union School District, Dehesa School District and Warner Unified School District announced they would be closed Thursday, according to the San Diego County Office of Education.

Four schools in the Cajon Valley Union School District were closed Thursday due to power outages and road closures. Those schools are Hillsdale Middle, Jamacha Elementary Rancho San Diego Elementary and Vista Grande Elementary.

The dry and windy weather pattern is likely to continue into next week, though likely in a weakened manner, forecasters said.

Updated at 8:25 a.m., Thursday, Dec. 3, 2020

— City News Service