Strong Santa Ana winds, triple-digit temperatures and low humidity will heighten the risk of “extreme fire behavior” in San Diego County for the fourth consecutive day Wednesday.

National Weather Service map showing areas of high heat (orange), and high winds (yellow) in the San Diego area.
National Weather Service map showing areas of high heat (orange), and high winds (yellow) in the San Diego area.

The National Weather Service first issued a red flag warning — its most serious fire-related warning — for valley and mountain areas on Sunday. That warning is scheduled to remain in effect until 8 tonight.

The NWS also issued a high wind warning for the valleys and mountains until 4 p.m., saying sustained winds of 25 to 35 miles per hour and gusts of 55 to 65 mph were likely. Isolated gusts of 75 to 85 mph were also possible on wind-prone mountain slopes, according to the agency.

A less-serious wind advisory was also in effect until 4 p.m. for coastal areas, where sustained winds of 20 to 30 mph and gusts up to 45 mph were expected today.

“The winds will make driving difficult, especially for motorists with high profile vehicles,” the weather service said. “Watch for broken tree limbs and other debris on roadways.”

In addition to the high wind warning, valley areas were subject to a heat advisory until 6 p.m. Thursday. The weather service said highs will be 97 to 102 degrees in the western valleys today and from 95 to 103 on Thursday.

“Take extra precaution if you work or spend time outside,” the weather service said. “When possible, reschedule strenuous activities to early morning or evening.”

Because of the weather, the Mountain Empire Unified School District in the far eastern reaches of the county announced all of its 10 schools would be closed today.

— City News Service

Chris Jennewein is founder and senior editor of Times of San Diego.