QUINCY, Calif. — The danger seemed like it was behind them.

Teresa Hatch, 61, had evacuated her rural Northern California town several days ago as the Dixie Fire menaced, but soon was allowed back. Then the alerts started lighting up her cellphone Wednesday, telling her to get out again — fast.

She said she grabbed her dog, Scooby, filled three plastic bags with clothes and hopped into the first car that passed.

Hatch, a fourth-generation Greenville resident, is among more than 18,000 people ordered evacuated around California as firefighters struggle to control two fast-growing wildfires. The Dixie Fire mushroomed in size overnight to become the largest wildfire burning in the United States and the third-biggest in California’s history, decimating century-old buildings in Hatch’s historic town. The smaller River Fire also threatened thousands of homes.

The Dixie Fire covers more than 432,000 acres in Butte and Plumas counties, rapidly expanding from about 362,000 acres Thursday evening and fueled by hot, arid and windy conditions. The wildfire was 35 percent contained by Friday, pushing toward firefighters’ control lines. Fire officials expressed hope Friday that higher humidity would help them counter the blaze.

“It’s kind of the perfect storm,” Yana Valachovic, forest adviser and county director at the University of California Cooperative Extension, said of the Dixie Fire. “We saw all this. The potential was high this year for these kinds of conditions, and once you get an ignition, especially in areas that are a little bit difficult to access and with new communities all around there, it stresses the system.”

The Dixie Fire’s status as California’s largest wildfire since last August is fueling concern in a year on track to break last year’s undesirable records. Climate change and a severe drought have worsened the state’s wildfire season, prompting alarms from scientists and concern about the challenging picture for firefighters and residents across the region.

For Greenville, any progress containing the fire will come too late. Little of the sparsely populated mountain town remained after flames reached it Wednesday evening.

The town library, torched. Abandoned cars, smoldering. The air, thick and gray.

“The Dixie Fire burnt down our entire downtown,” Plumas County Supervisor Kevin Goss wrote on Facebook. “Our historical buildings, families homes, small businesses, and our children’s schools are completely lost. Every square inch of downtown holds countless memories for each member of our small community and ample amount of history from our ancestors.”

The Dixie Fire has destroyed roughly 91 buildings and damaged five others since it broke out more than three weeks ago, officials said. In Greenville, the U.S. Forest Service estimated that only about a quarter of structures had been saved. Among them were a Dollar General store and Greenville High School.

In Quincy, about 26 miles south, Hatch huddled Friday at a Red Cross shelter with her family. She said she went to a friend’s house for coffee Wednesday morning and returned home to see “a ball of flames” behind a nearby mountain.

When the evacuation order came hours later, she called her 38-year-old daughter Ellie and roused her from her sleep. The pair left town with Ellie’s father, David, bought three tents at a local store and are sleeping outside in Quincy.

“I just want to go home,” she said with tears in her eyes.

Richard Foriskee, 78, who has lived in Greenville for 21 years, made his way to the shelter as well. He said he escaped with only his car, three sets of clothes, a sleeping bag and his birth certificate.

Foriskee, a plasterer by trade, said he had also evacuated previously and was allowed to return. The rain cut some of the heat from the air. But Wednesday was different.

“You could tell it was different by the smoke and the heat coming in,” Foriskee said. “There’s that glow and you know it’s bad. You don’t have to be told. You just understand.”

Greenville, with about 1,100 residents as of 2010, has a storied history. It was home to the Maidu tribe of Native Americans for centuries before European settlers arrived in the 1850s amid the Gold Rush. The town was named after the Green family, who ran a boardinghouse offering hot meals to the growing town.

Greenville’s gold mines drew more settlers and merchants throughout the decade, and the town grew to boast a church, a school, general stores, hotels and saloons. Then another fire ravaged the area, destroying many of those buildings and forcing residents to rebuild.

Before the Dixie Fire, only a handful of buildings in Greenville’s quaint downtown were less than 50 years old, according to the Indian Valley Chamber of Commerce. Chain stores and restaurants were completely absent. Although the town’s economic engine was historically powered by mining, logging and ranching, more recently it has been supported mostly by tourism and recreation.

California’s Dixie Fire has burned for more than three weeks, scorching at least 440,000 acres as of Aug. 7. (Reuters)

Now, Greenville is a ghost town. More than 7,000 people in surrounding Plumas County had been evacuated by Friday, and officials added new evacuation orders for adjacent Lassen County.

About 11,000 people elsewhere in the state also fled as other wildfires threatened their homes. About 40 miles northeast of Sacramento, the River Fire burned 2,600 acres and was about 30 percent contained.

More than 100 wildfires are active across the country, with 11 new ones erupting Thursday in Alaska, Oregon, Idaho, Washington, Montana and Wyoming.

While the Dixie Fire has proved to be fast-growing, Valachovic said it isn’t unique. Rather, she said, it exemplifies how significant drought, dry lightning strikes and parched vegetation primed California and other Western states for a dire wildfire season.

Stretched-thin firefighting resources and recurring heat waves have further complicated the situation. Valachovic said the Dixie Fire’s devastation underscores the importance of both wildfire prevention and active firefighting.

“We need to invest in prevention and restoration of our forests and all the things that we recognize are important for creating resilience,” she said.

Hatch said she doesn’t know how Greenville, which she said is home to many low-income residents, will rebuild.

“I’m okay losing everything, but what do I do now?” she asked. “Where do I go?”

correction

A previous version of this report incorrectly identified the U.S. Forest Service as the U.S. Fire Service. It has been corrected.