The blaze, which erupted in the Stanislaus National Forest north of the Tuolumne River, has destroyed 111 buildings, including 11 homes and three businesses.
The cost of fighting the fire reached $84.8 million Friday. Six people have been injured. It started when a hunter let his illegal campfire get out of control, federal forest officials said.
About 1,900 structures remain threatened. About 3,600 firefighters are still in the area, down from more than 5,100.
Despite the fire being 80% contained, officials said they expect it to intensify as the flames burn through remaining vegetation within its interior.
Authorities opened the western section of California 120 into Yosemite National Park on Friday.
Visitors will have full access to Yosemite Valley from the park's western entrance from Groveland for the first time since the Rim fire broke out Aug. 17.
Though a 14-mile stretch of the highway is closed within the park — from Crane Flat to White Wolf — the update was met with joy Friday.
Linda Struhm, who works at the front desk of the Hotel Charlotte in Groveland, was ecstatic.
"Did you hear? It's official. They're opening the road!" she told her friend, a real estate agent. "Yay! Yay! Yay!"
Struhm said traffic would have been nonstop last weekend over the Labor Day holiday as people headed to the park. Instead, the highway through town was all but empty.
Under blue skies Friday morning, she warned a family from Switzerland heading to the park to not get out of their car and walk around in the burn area.
"Use caution. But just drive straight through to Yosemite and enjoy," she said. "This is big. This is great."
Authorities cautioned that stopping along the highway is prohibited and all access points to secondary roads remained closed.
The Rim fire has burned 246,350 acres, or 385 square miles, the U.S. Forest Service said Friday. It surpassed the 2007 Zaca fire in Santa Barbara County for the third spot.
A burn operation to cut off the fire's path south near California 120 was successful Thursday, and crews were planning on spending Friday searching out small spot fires.
Marcum reported from Groveland, Calif., and Serna from Los Angeles.