Red flag warnings for fire danger are going into effect Monday for mountains north of Los Angeles and to the west in Ventura County as well as the high desert Antelope Valley. More high heat is in store for much of Southern California, especially interior areas.
The National Weather Service says gusty onshore winds, very low relative humidity and hot temperatures will keep the warnings in effect until 9 p.m. Thursday.
Much of the rest of inland Southern California has elevated fire danger due to the continuing heat wave.
The Los Angeles County Fire Department brought in extra staff throughout the county for Monday and Tuesday to the fire weather warnings, L.A. County Fire Inspector Gustavo Medina tells KPCC. They also have extra water tenders and patrol strike teams ready to go.
Areas with extra staff include Rancho Palos Verdes, Claremont, Malibu and other desert areas, Medina says.
“In case anything happens in high volatile areas, such as Santa Clarita or Malibu, they’ll be ready," Medina says.
That extra staffing is likely to continue during the week ahead, Medina says.
“We hope we don’t get a brush fire, but you just never know," Medina says.
The current heat wave is due to an area of high pressure across southwestern California, the Weather Service's Robbie Munroe tells KPCC. He explained how that works.
"An area of high pressure is an area of sinking air, and what that does it helps to dry out and heat up the air at the surface," Munroe says. "As the air sinks, it compresses, and it makes the molecules move faster, and heats things up that way."
The National Weather Service says the scenario is due to an upper-level high-pressure system combined with weakening onshore flow near the surface.
Triple digit heat is expected across the warmest portions of the valleys, foothills and lower mountains through Tuesday. Still, things should cool soon.
"It looks like we're going to get a break from the heat by the middle of this week, as we actually have a weak low-pressure system moving off the southwestern California coastline, and so we're expecting temperatures to resume to near normal, likely lasting into this weekend," Munroe says.
He added an explanation for what goes into low-pressure cooling.
"Low pressure is associated with rising air, and that also is accompanied by cooler air aloft, especially this time of year, and that helps cool things off at the surface," Munroe says.
A large swath of San Bernardino, Riverside, Orange and San Diego counties are under a heat advisory and Imperial County in the southeast corner of the state is under an excessive heat warning.
Forecasters say inland areas of the coastal plain will also be very warm, ranging from 85 to 95 degrees.
The heat, low humidity levels and very dry fuels will combine to raise the danger of wildfires.
This story has been updated.