The Thomas fire in Ventura and Santa Barbara counties has consumed 230,000 acres in the past week.
Fanned by strong winds, it has become the fifth largest wildfire in recorded state history after it grew by more than 50,000 acres in a day.
Residents in coastal beach communities have been ordered to leave.
On Sunday, firefighters reported that 15 percent of the blaze had been contained but were forced to downgrade that to 10 percent as it continued to spread.