Forecast humidity on Friday
Forecast humidity on Friday. Courtesy National Weather Service

The National Weather Service office in San Diego warned residents that the first major Santa Ana wind event of the season will begin Wednesday night and continue through Friday.

The weather service issued a fire weather watch amid a forecast of single-digit humidity and gusty winds of up to 60 mph.

“Periods of strong and gusty Santa Ana winds will develop late Wednesday night in the San Bernardino County mountains and valleys, then spread southward into the San Diego County mountains and valleys Thursday morning, with the winds becoming more widespread Thursday afternoon,” the weather service said.

Primarily affected will be areas along and below coastal mountain slopes, including the western parts of the inland valleys, as wells as canyons and passes, with some areas expected to be under a red flag warning by Thursday afternoon.

Humidity will drop to under 10 percent on Friday, with poor overnight recovery and a warming trend.

“This will cause critical fire weather conditions for Thursday into Friday for much of extreme southwestern California,” the weather service said. “Any fires that develop will likely spread rapidly.”

High temperatures Wednesday could reach 75 degrees near the coast and inland, 80 in the western valleys, 78 in the mountains and 98 in the deserts.

Updated at 3:15 p.m., Tuesday, Oct. 8, 2019

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