LOS ANGELES --
A Red Flag Warning signifying a high risk of wildfire was in effect Wednesday in the mountains and forests of Southern California because of high heat and low humidity.
High pressure building over the region will drive a warming trend as summer arrives, and the relative humidity in the already parched mountains will drop to 10 percent or lower for periods up to 15 hours long, according to the National Weather Service.
The alert covering mountains from Ventura County to the Mexico border will be in effect through Thursday morning.
In the region's northern reaches, the Red Flag Warning is limited to elevations above 4,000 feet.
The fire danger will be highest above elevations moistened by the marine layer, said Stan Waskowski of the NWS office serving Orange and San Diego counties.
"The inversion layer comes in around 1,500 feet and that helps keep the humidity up," he said.
The Southland is suffering from its driest "wet" season on record. Only 3.2 inches of rain has fallen in Los Angeles since July 1.
The Warning was scheduled to expire at 5 a.m. in Los Angeles, Ventura and Santa Barbara counties and 9 a.m. in Orange, San Diego, Riverside and San Bernardino Counties.
The warning is scheduled to expire at 5 o'clock Thursday morning.
