Yosemite National Park, CA (CNN) — A northern California wildfire that's threatening Yosemite National Park grew to historic proportions early Monday, becoming the 13th largest in state history, state fire authorities said.
The sprawling Rim Fire, which has devoured more than 149,000 acres, has scorched an area about the size of the city of Chicago while more than 3,400 firefighters try to rein it in.
Susan Loesch and Curtis Evans just started settling into their second home in California's Sierra foothills a few months ago. Now, they're worried it could go up in smoke as the massive wildfire spreads.
"This is kind of a little paradise up here for us. ... To think this would all be gone would be devastating," Evans told CNN on Sunday.
Cradling their Chihuahua, Cuervo, they prepared to leave the area Sunday.
"It's scary," Loesch said. "You worry about the firefighters being on the line. ... It's overwhelming."
The wildfire, which was 15% contained Monday morning, according to California's Department of Forestry and Fire Protection, was spreading primarily to the northeast and east and threatened to grow amid extremely dry conditions and hot weather.
After days of battling the blaze, things were starting to look up Sunday, said Vickie Wright, a spokeswoman for the U.S. Forest Service.
"We're a long way from complete," she said, "but at least our boots on the ground are getting a better handle on it."
Several helicopters and air tankers were aiding firefighting efforts.
A top priority is stopping the fire from spreading further in Yosemite National Park.
"The park is a national treasure," Wright said, "so no matter what it takes, we're going to do everything in our power to protect that park."
While the Rim Fire has consumed at least 12,000 acres in the northwest section of the park, so far it has had little or no direct impact on Yosemite Valley, a popular spot for tourists and home to many of the famous cliffs and waterfalls in the park.
About 4,500 structures, many of them vacation homes, were under threat, according to InciWeb, a federal website that collects information from agencies such as the U.S. Forest Service and Bureau of Land Management.
The inferno threatened the Yosemite gateway communities of Groveland and Pine Mountain Lake just outside the Stanislaus National Forest.
The Tuolumne County Sheriff's Office, meanwhile, issued evacuation advisories for the town of Tuolumne and nearby Ponderosa Hill, InciWeb said. It was not clear how many residents were covered by the evacuation advisory.
Authorities say the Rim Fire started on August 17. The cause is under investigation.
Fire, what fire?
The park typically has 15,000 visitors on a busy summer weekend. August sees an influx of visitors from other countries, a few of whom have called to check on conditions.
Still, there's little indication so far it's keeping many people away.
Ranger programs went on as normal over the weekend and campgrounds were full.
"If somebody cancels, there are 10 people that will take their spot," said Yosemite spokesman Scott Gediman.
Yosemite, with hundreds of campground sites and lodging units, had nearly 4 million visitors last year, the National Park Service said.
--CNN's Nick Valencia and Gary Tuchman reported from Yosemite National Park, and Catherine E. Shoichet and Phil Gast reported and wrote in Atlanta. CNN's AnneClaire Stapleton contributed to this report.