With scant cooperation from Mother Nature, fire crews waged a battle with few gains Sunday against the giant Rim Fire, which voraciously consumed dry brush and trees as it marched toward the Hetch Hetchy reservoir in Yosemite National Park.

As of Sunday evening, the fire had burned 224 square miles -- more than the area occupied together by San Jose, Santa Clara, Sunnyvale and Campbell. It remained only 7 percent contained. Nearly 2,850 firefighters from the U.S. Forest Service, Cal Fire and numerous local agencies were battling California's largest wildfire. Southerly afternoon winds up to 20 miles per hour pushed the fire north, said Cal Fire Captain Mike Mohler.

If there was any good news, it was that the predicted gusts up to 30 mph didn't materialize. But the bad news is that high temperatures, in the mid-80s Sunday, are expected to rise Monday.

"With the size of the fire and amount of ground we still have to cover, it's still a difficult fire," Mohler said. "We need Mother Nature to cooperate. Hopefully we'll turn the corner soon."

The Rim Fire also threatened communities to the south of Highway 120 in Mariposa County, with evacuation orders issued at 5 p.m. In addition, recommended evacuation remained in place for several mountain communities in Tuolumne County, including Camp Mather and San Jose Family Camp. The Red Cross was operating a shelter at the Mother Lode Fairgrounds in Sonora, said Carole Logue, a volunteer with the Tuolumne County Office of Emergency Services.

Bay Area threat

Aside from the rugged and hard-to-reach terrain, another difficulty is the blaze's tendency to burn the tops of trees, creating a "crown fire" with long, intense flames that skip across forested land faster than a wildfire that creeps along near the ground.

Courtesy of southerly winds, Yosemite National Park remains open and is relatively smoke-free, according to the park website. But the entrance from Highway 120 on the west side of the park, the White Wolf campground, the Hodgdon Meadow campground and the Hetch Hetchy backpackers' campground were closed as of Sunday evening.

Popular areas in the park such as Yosemite Valley, Glacier Point, Wawona, Mariposa Grove, Crane Flat and Tuolumne Meadows were open Sunday.

Although the Rim Fire is more than 100 miles from the Bay Area, it still could threaten San Francisco's electric supply if it damages the power system originating in O'Shaughnessy Dam at Hetch Hetchy reservoir. The San Francisco Public Utilities Commission has been forced to shut down two of its three hydroelectric power stations near Hetch Hetchy, and Gov. Jerry Brown has extended a state of emergency to include San Francisco because the reservoir is a major source of electricity and water for the city.

As fire leapfrogs across the vast, picturesque Sierra forests, moving from one treetop to the next, residents in the fire's path are moving animals and children to safety.

"Left everything"

The fire moved through San Jose Family Camp last week, consuming an outbuilding and 10 tents, said camp recreation Supervisor Art Catbagan. He said he was hoping that a group from Maybeck High in Berkeley, which evacuated on 15 minutes' notice, could return early this week to recover belongings.

"They left everything -- books, clothing, things on their beds. They even had food in the cafeteria they were getting ready to prepare," Catbagan said.

The fire has burned northeast away from Groveland, where smoke gave way to blue skies Sunday. But at Tuolumne City's Black Oak Casino in Tuolumne City, the slot machines were quiet as emergency workers took over nearly all of the resort's 148 hotel rooms.

"The casino is empty," said casino employee Jessie Dean, who left her four children at relatives' homes in the Central Valley. "Technically, the casino is open, but there's nobody there."

Hundreds of firefighters were deployed Sunday to protect Tuolumne City and other communities in the fire's path. Eight fire trucks and four bulldozers were deployed near Bunney's ranch on the west side of Mount Baldy, where two years of drought have created tinder-dry conditions.

The Los Angeles Times and The Associated Press contributed to this story. Contact Sharon Noguchi at 408-271-3775. Follow her at Twitter.com/NoguchiOnK12.