GREENVILLE, Calif. (AP) — A 3-week-old wildfire engulfed a tiny Northern California mountain town, leveling most of its historic downtown and leaving blocks of homes in ashes, while a new wind-whipped blaze also destroyed homes as crews braced for another explosive run of flames Thursday in the midst of dangerous weather.

The Dixie Fire, swollen by bone-dry vegetation and 40 mph (64 kph) gusts, raged through the northern Sierra Nevada community of Greenville on Wednesday evening. A gas station, church, hotel, museum and bar were among many fixtures gutted in the town, which dates to California's Gold Rush era and had some structures more than a century old.

The fire “burnt down our entire downtown. Our historical buildings, families homes, small businesses, and our children’s schools are completely lost," Plumas County Supervisor Kevin Goss wrote on Facebook. The sheriff's department said there was “widespread devastation throughout the area."

“We lost Greenville tonight,” U.S. Rep. Doug LaMalfa, who represents the area, said in an emotional Facebook video. “There's just no words.”

As the fire’s north and eastern sides exploded Wednesday, the Plumas County Sheriff’s Office issued a warning online to the town’s approximately 800 residents: “You are in imminent danger and you MUST leave now!”

A similar warning was issued Thursday for residents of another tiny mountain community, Taylorsville, as flames pushed toward the southeast. To the northwest, crews were protecting homes in the town of Chester. Thousands remained under evacuation orders or warnings.

The growing blaze that broke out July 21 is the state’s largest current wildfire and had blackened over 504 square miles (1,305 square kilometers), territory larger than the city of Los Angeles. The cause is under investigation but Pacific Gas & Electric has said it may have been sparked when a tree fell on one of its power lines.

The fire was burning near the town of Paradise, which largely was destroyed in a 2018 wildfire that became the nation’s deadliest in at least a century and was blamed on PG&E equipment.

Ken Donnell left Greenville on Wednesday, thinking he’d be right back after a quick errand a few towns over. He was unable to return as the flames swept through. All he has now are the clothes on his back and his old pickup truck, he said. He’s pretty sure his office and house, with the go-bag he had prepared, is gone.

Donnell remembered assisting victims of 2018’s devastating Camp Fire, in which about 100 friends lost their homes. “Now I have a thousand friends lose their home in a day,” he said. “We’re all stunned.”

By Thursday, the Dixie Fire had become the sixth-largest fire in state history, the California Department of Forestry and Fire Protection said. Four of the state's other five largest wildfires were all in 2020.

To the north, Lassen Volcanic National Park was closed to all visitors.

There were no immediate reports of injuries or deaths. Dozens of homes had already burned before the flames made a new run on Wednesday.

“We did everything we could,” fire spokesman Mitch Matlow said. “Sometimes it’s just not enough.”

About 100 miles (160 km) to the south, officials said between 35 and 40 homes and other structures burned in the fast-moving River Fire that broke out Wednesday near Colfax, a town of about 2,000. Within hours it ripped through nearly 4 square miles (10 square kilometers) of dry brush and trees. There was no containment and about 6,000 people were under evacuation orders across Placer and Nevada counties, according to Cal Fire.

In Colfax, Jamie Brown ate breakfast Thursday morning in a downtown restaurant while waiting to learn if his house was still standing or not.

He evacuated his property near Rollins Lake on Wednesday when “it looked like the whole town was going to burn down.” Conditions had calmed a bit by Thursday and he was hoping for the best.

“I figure I better have a nice breakfast before I lose my home,” he said. “My house is right in the way if the wind puts the fire on a separate path.”

After firefighters made progress earlier in the week, red flag weather conditions of high heat, low humidity and gusty afternoon and evening winds erupted Wednesday and were expected to be a continued threat.

Winds were expected to change direction multiple times on Thursday, putting pressure on firefighters at sections of the fire that haven’t seen activity in several days, officials said.

The trees, grass and brush were so dry that “if an ember lands, you’re virtually guaranteed to start a new fire,” Matlow said.

And about 150 miles (240 kilometers) to the west of the Dixie Fire, the lightning-sparked McFarland Fire threatened remote homes along the Trinity River in the Shasta-Trinity National Forest. The fire was only 7% contained after burning through nearly 33 square miles (85 square kilometers) of drought-stricken vegetation.

Similar risky weather was expected across Southern California, where heat advisories and warnings were issued for interior valleys, mountains and deserts for much of the week.

Heat waves and historic drought tied to climate change have made wildfires harder to fight in America's West. Scientists say climate change has made the region much warmer and drier in the past 30 years and will continue to make weather more extreme and wildfires more frequent and destructive.

More than 20,000 firefighters and support personnel were battling 97 large, active wildfires covering 2,919 square miles (7,560 square kilometers) in 13 U.S. states, the National Interagency Fire Center said.

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Weber reported from Los Angeles. Associated Press writers Janie Har and Jocelyn Gecker in San Francisco also contributed.