CalFire says the rugged terrain is making it difficult for its crews to reach the flames.
RELATED: Track wildfires across Bay Area, other parts of California with this interactive map
The wildfire, called the Dixie Fire, is now 12% contained. That's a 3% improvement from earlier Saturday morning.
Evacuations remain in place, but firefighters are hopeful nearby neighborhoods are safe.
No buildings have been lost.
Firefighters say instead of digging new containment lines, they've been able to re-enforce some of the ones they dug for the Camp Fire in 2018, which has saved them some time.
VIDEO: Fire Weather Watch issued for parts of Bay Area this weekend due to possible dry thunderstorms
Fire Weather Watch issued for parts of Bay Area this weekend