The huge Rim fire raging near Yosemite National Park continued to grow Monday night, but firefighters also made progress in containing the blaze.
The wildfire was threatening 4,500 structures as flames consumed brush and timber in an area larger than the city of Chicago, state fire officials said. At least 23 structures have been destroyed.
A new evacuation advisory was issued to the west of the blaze along a stretch of California 108 from Long Barn to Pinecrest in the Stanislaus National Forest, fire officials said Monday night.
On Monday night, the blaze was 20% contained and had grown to nearly 161,000 acres, according to the California Department of Forestry and Fire Protection. Earlier Monday, the blaze was 149,780 acres.
Fire officials said flames remained intense as night fell on the area, but they were hoping that higher humidity would help the thousands of firefighters who are battling the blaze.
Humidity was 60% Monday night, but winds were blowing out of the southwest at 15 mph.
The blaze, which broke out Aug. 17, was still spreading to the north and northeast into old growth timber in the Stanislaus National Forest, the U.S. Forest Service said.
The flames have also raged into Yosemite, burning nearly 22,000 acres of parkland as of Monday afternoon, officials said.
More than 3,600 firefighters on the ground were being aided earlier in the day by helicopters and fixed-wing aircraft, including huge DC10 bombers that made repeated assaults on the fire front.
Fire officials credited the air attack with helping them along the western flank of the blaze near Tuolumne, in an area that fire commanders have referred to as the California 108 corridor.
Earlier Monday, when the Rim fire was 15% contained, fire officials said they were pleased with the progress made by crews cutting fire breaks around the huge blaze.
"Everything is looking as good as it possibly can for this stage of the fire," said Johnny Miller, a spokesman with the Cal Fire. "We're making good progress."
Temperatures in the Yosemite Valley region were expected to remain in the mid-90s this week. Officials at Yosemite said campgrounds have been packed and that the popular Yosemite Valley and much of the park are free from smoke.
On Monday, Brown toured the devastation and met with fire commanders and first responders. The governor said President Obama had called him to express support and offer assistance.
"This is something that we have to live with -- it may even get worse in years to come -- but California will be ready for it," Brown said at a news conference.