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California's wildfire season is off to a scorching start, with more than twice as many acres burned in the first six months of 2017 than at this point last year, officials said Monday.

Amid blazing temperatures, 633 new wildfires started last week alone across a state stricken by five years of drought, San Diego County Fire Chief Tony Mecham said in a statement.

Among them were the Alamo Fire, which had burned through nearly 30,000 acres of the state's central coast and was 15 percent contained by Monday afternoon, and the Whittier Fire, which had torn through nearly 11,000 acres in nearby Los Padres National Forest and was 5 percent contained.

On Sunday, the Whittier Fire swept through The Outdoor School, a Boy Scouts summer camp in Los Padres, killing all of the animals in its nature center.

Smoke from the Whittier wildfire near Santa Ynez, California, on Saturday. Michael Nekrasov / via Reuters

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"While this fire is utterly devastating, those that hold true to the magic and wonder that this place has instilled in our youth will continue to inspire for years to come," the Outdoor School said in a statement.

Photos: Raging Wildfires Threaten Hundreds of Homes in California

North of Sacramento, Gov. Jerry Brown issued a state of emergency on Sunday in Butte County over the Wall Fire, which had burned 5,600 acres by Monday. Nearly as many structures remained under threat, and roughly 4,000 people had been evacuated.

Among those in the fire's path was Monica Hardeman, owner of a sanctuary for abused and abandoned horses. On Sunday, amid unpredictable winds and a fire that seemed to constantly change its course, Hardeman refused to leave the 15 horses that hadn't yet been evacuated, NBC affiliate KCRA of Sacramento reported.

"My job is to protect them," she said. "I can't imagine them not being saved."

Firefighters remove a U.S. flag as flames from the "Wall Fire" close in on a luxury home in Oroville, California on July 8, 2017. The first major wildfires after the end of California's five-year drought raged across the state on July 8, as it was gripped by a record-breaking heatwave. Josh Edelson / AFP - Getty Images

By Sunday, 2,905 fires had scorched nearly 70,000 acres across the state, compared to just 2,200 fires that burned 30,000 acres during the first six months of 2016, according to the state's fire agency, CalFire.

CalFire spokesman Michael Mohler attributed the dramatic rise, in part, to the torrential rains that soaked the state last winter — and all the grass that grew in the spring. At the same time, the bark beetle has taken advantage of the drought, boring into the veins of more than 100 million defenseless trees across the state.

"That takes its life away," Mohler told NBC News.

The combination has left the state's wildfires with plenty of fuel, he said. And it could just get worse in counties like Fresno, which have been especially hard hit by the bark beetle.

"If we have a fire there, it's going to be massive operation," he said.