IDYLLWILD, Calif. (AP) — Calm conditions aided firefighters early Thursday on the lines of a suspected arson wildfire that forced thousands of people to flee mountain communities east of Los Angeles, while in a far northern region of California firefighters battled a week-long blaze that suddenly ballooned.

Winds were absent over the fire in Southern California's San Jacinto Mountains but temperatures were rapidly rising and forecasters said highs could hit 100 degrees (38 Celsius). They also warned of possible afternoon wind gusts that could create dangerous fire weather conditions.

Hundreds of miles to the north, however, new evacuations were ordered for communities in the wilderness recreation region near Whiskeytown Lake as that wildfire tripled in size to more than 31 square miles (80 square kilometers). It had already forced residents out of French Gulch, a hamlet dating to the Gold Rush.

"Last night it made a huge push," Cal Fire Unit Chief Mike Hebrard told the Record Searchlight newspaper, adding that engine crews were in the community of Old Shasta trying to save structures.

Elsewhere in the state, a huge forest fire continued to grow outside Yosemite National Park and 100 homes were still considered under threat in the San Francisco Bay community of Clayton although firefighters had stopped the progress of a small fire there after one house burned.

The blaze in the San Jacinto Mountains erupted Wednesday and quickly turned into a wall of flame that torched timber and tinder-dry brush. In a matter of hours it grew to 7.5 square miles (19 square kilometers).

About 3,200 people in the town of Idyllwild and nearby communities were ordered to evacuate. An estimated 600 homes were threatened.

The fire was the largest of at least five that police believe were purposely set Wednesday by a man whose car was reportedly spotted at the starting point of the blaze in Riverside County, officials said.

Brandon N. McGlover, 32, of Temecula was booked on suspicion of five counts of arson, state fire officials said. It wasn't clear whether he had an attorney.

Authorities ordered residents to leave Idyllwild and several neighboring communities, home to about 12,000 people.

William Blodgett of Idyllwild said he couldn't get home because of the fire and had to wait along with others at a gas station in nearby Mountain Center — until the fire hopped a highway and began to move in his direction.

"We were all peeling out of there as fast as we could," he told KNBC-TV. "It was apocalyptic."