A 160-acre brushfire was burning Saturday afternoon along a cove at Lake Castaic.
It was reported by lifeguards just after 4 p.m. as a 1/4-acre brushfire, which quickly spread to 20 acres, said Los Angeles County Fire Department officials.
A helicopter over the fire reported it had a potential to spread to 200 to 300 acres.
Just after 5 p.m., the U.S. Forest Service reported the fire had blackened 150 acres of forest service land, spreading through dry brush with high temperatures and low humidity. No structures were threatened. That figure was quickly upgraded to 160 acres.
The National Weather Service reported the temperature was 95 degrees with southwest winds at 13 mph with gusts to 19 mph and humidity at 21%.
The L.A. County Fire Department is assisting the USFS, which reported three helicopters and four fixed-wing aircraft were assigned to the blaze.