The brush fire, which erupted on Wednesday in the San Bernardino Mountains, was 24 percent contained as firefighters attacked the flames with a fleet of water-dropping aircraft.
"It's starting to behave itself a little bit, and we're catching up and getting around it," said Lee Beyer, a spokesman for crews fighting the fire.
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Fire officials say most of the area has not burned in 100 years.
The National Weather Service in Oxnard said a high pressure system that pushed temperatures into the triple digits in Southern California over the weekend was drifting east, allowing a gradual cooling trend into the middle of the week.
The cause of the fire has not been determined. The estimated cost has reached $6.8 million.
No structures have been damaged or destroyed, and no injuries were reported.
The Associated Press contributed to this report.