Evacuation orders affected some 2,200 homes and 6,000 residents and visitors, said US Forest Service spokeswoman Carol Jandrall.
Winds that were moving the fire into wilderness were beginning to change direction, said Forest Service spokeswoman Melody Lardner.
Very hot and dry conditions were forecast for the next two days, said Tina Rose, a spokeswoman for the California Department of Forestry and Fire Protection.
Rose said the fire was showing extreme behavior in an area that hadn't burned in many years.
"The slightest little spark is going to make a run and torch trees," Rose said. "It's just so bone dry."
The wildfire started Monday. Nearly 3,000 firefighters and 25 aircraft had the blaze about 15 per cent contained.