The fire has blackened 301 square miles and is 30 percent contained as of Thursday morning.
Even though the blaze grew by a few hundred acres overnight, officials remain confident about their efforts to corral the wildfire.
"We remain very optimistic that our containment lines are holding, and we'll continue to strengthen lines around communities that are threatened around the fire," said California fire spokesman Daniel Berlant.
Fire officials said they expect to fully surround the fire in about three weeks, although it will burn for much longer than that, possibly until the state's dry season ends this fall.
"My prediction is it will burn until we see rain," said Hugh Safford, a regional ecologist with the U.S. Forest Service.
Officials worry that smoke from the fire will continue affecting air quality north of Yosemite in the Lake Tahoe basin and neighboring Nevada.
The California National Guard deployed a drone on Wednesday that was being remotely piloted hundreds of miles away. The drone, the size of a small Cessna, will remain over the burn zone for up to 22 hours at a time, allowing fire commanders to monitor fire activity and confirm new fires ignited by lightning or flying embers.
The Rim Fire started Aug. 17 and quickly exploded in size. Its progression slowed earlier this week when it moved from parts of the forest with thick underbrush that had not burned in nearly a century to areas that had seen fire in the past two decades.
Officials say the Rim Fire has destroyed 111 structures, including 11 homes, and threatened ancient giant sequoias.
The fire also has threatened San Francisco's water supply at the Hetch Hetchy Reservoir, but Safford said it was burning itself out as it approached and that crews were lighting back burns to push it back into the wilderness.
The Associated Press contributed to this report.
