The fire was estimated at around 2,500 acres on Monday morning, two days after it began. It was 10 percent contained.
Fire information officer Adrienne Freeman says it is burning in steep terrain and has been aided by high temperatures and dry conditions.
More than 300 firefighters are working on the blaze. The cause has not been determined.
Crews are also battling a separate blaze several miles to the east in Colusa County.