An increased risk of wildfire will threaten much of San Diego County this week as dry, hot and windy conditions develop in the inland valleys and local mountains.

“High pressure aloft will strengthen along the West Coast through Thursday, bringing much warmer daytime temperatures,” according to the National Weather Service. “Surface high pressure over the Great Basin will bring periods of strong gusty east to northeast winds through Wednesday … along with low humidities.”

National Weather Service map for San Diego region for May 12.
National Weather Service map for San Diego region for May 12.

The agency said the most significant combination of hot daytime temperatures, very low humidity and strong gusty Santa Ana winds is expected on Tuesday and Wednesday, though Wednesday’s winds will be weaker and will diminish faster.

A red flag warning for inland valley and mountain areas is in effect until 8 p.m. Tuesday. According to the weather service, during that time there will be sustained northeast to east winds of 15 to 25 miles per hour and gusts to 45 mph, mainly along coastal slopes and below passes and canyons. The humidity is expected to be around 5 percent.

A red flag warning is the NWS most serious fire-related warning.

“It will continue to be hot and very dry Thursday, but with weakening winds,” the NWS said.

Highs around the region today are expected to be mainly in the high 80s to low 90s. By Wednesday, triple-digit temperatures are likely.

A cooling trend is expected by the weekend.

— City News Service

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