Fire officials said Monday that 12 helicopters and 967 firefighters are battling the 3,800 acre Hathaway Fire in Riverside County in heavy chaparral and timber.
The National Weather Service issued a red flag warning for the Los Angeles and Ventura county mountains as several fires continued to burn in the region.
Meteorologist Stuart Seto said the combination of gusty winds and low humidity will create heightened fire danger conditions.
"Some of the bigger problems have been when there's dry grass along the roadways and people pull off and the hot mufflers or the catalytic converters will ignite the grass," Seto said. "Keep the cigarettes inside the car and the butts — put them out in the ash tray — and all precautions, you know, relating to sparks, especially with machinery and stuff like that and dry grassy areas, should be avoided."
The red flag warning was set to go into effect Wednesday morning and last through late Thursday morning.
There was also a high wind warning in effect for the L.A. County mountains. That one was set to last through noon Wednesday. Winds are expected to gust up to 50 mph.
The red flag warning could not have been welcome news for crews that continue to battle wildfires in Southern California.
Firefighters have increased their edge on the Hathaway Fire, which started on June 9 on a portion of the Morongo Indian Reservation, but it threatens to push and grow eastward into the San Gorgonio Wilderness, according to the latest information from fire authorities' official incident tracking website.
As of Tuesday night, firefighters had increased containment to 80 percent and stopped the fire from spreading for the time being.
The Hathaway Fire has so far burned more than 3,800 acres and almost 600 firefighting personnel are still on scene.
Meanwhile, crews were battling a separate brush fire Tuesday afternoon in Ventura County that had burned about 20 acres, according to the Los Angeles Times.
About 75 firefighters were on the ground or en route to the Condor fire, which broke out shortly before 4 p.m. east of Fillmore near Highway 126, the Times reported.