Thousands of firefighters battling a wildfire in northern California received some help from the weather Saturday morning, just hours after the blaze exploded in size, sending massive, swirling plumes skyward and scorching an area about the size of Los Angeles. The blaze was one of several fires tearing through the western United States and Canada, fueled by wind and heat.

Cooler temperatures and an increase in humidity on Saturday could help slow the Park Fire, the largest blaze so far this year in California. A man suspected of starting the fire has been arrested, which started in a park on Wednesday afternoon and grew from about 6,400 acres to a staggering 239,100 acres by Friday.

Weather conditions are easing up, but that may or may not have an impact on the fires, said Marc Chenard, a meteorologist at the National Weather Service Weather Prediction Center in College Park, Maryland.

Temperatures are expected to be cooler than average through the middle of next week, but “that doesn’t mean that fires that are existing will go away,” he said.

More than 130 structures have been destroyed so far, and thousands more are threatened as evacuations were ordered in four California counties: Butte, Plumas, Tehama and Shasta.

Authorities said a man pushed a burning car around 3 p.m. Wednesday in the upper part of Bidwell Park in Chico and then calmly blended in with others fleeing the scene. The car went up into flames completely sparking the larger fire. Officials later identified the suspect as 42-year-old Ronnie Dean Stout II. A local judge issued an arrest warrant and Stout was booked into jail. 

“It’s going to be another dynamic day,” Cal Fire incident commander Billy See said at a briefing on Saturday.

He noted that the blaze had been advancing 8 square miles per hour since its inception. However, there was cautious optimism as weather conditions slowed the fire’s advance in some areas, and firefighters were able to plan and deploy additional personnel.

“Today we’ve got almost three times the personnel we had yesterday morning,” he said. “We still don’t have enough.”

He advised his crews to be aggressive and safe and take advantage of what likely are the best conditions they will experience in the coming days.

More than 110 active fires covering 2,800 square miles were burning in the U.S. on Friday, according to the National Interagency Fire Center. Some were caused by the weather, with climate change increasing the frequency of lightning strikes as the region endures record heat and bone-dry conditions.

Amanda Brown, who lives in the same community where Stout was arrested, said she was stunned that someone would set a fire in a region where the memories of the devastation in Paradise are still fresh.

“That anyone could deliberately put our community through that again is incredibly cruel. I don’t understand it,” said the 61-year-old Brown, who was about a mile from the fire but had not been ordered to evacuate.

Elsewhere, fire crews were making progress on another complex of fires burning in the Plumas National Forest near the California-Nevada line, said Forest Service spokesperson Adrienne Freeman. Traffic was backed up for miles near the border on a portion of the main highway linking Los Angeles and Las Vegas, as crews continued Saturday to battle a fire that started a day before when a truck carrying lithium-ion batteries crashed and turned onto its side.

Evacuee Sherry Alpers, fled with her 12 small dogs and made the decision to stay in her car outside a Red Cross shelter in Chico after learning that animals would not be allowed inside. She ruled out traveling to another shelter after learning the dogs would be kept in cages, since her dogs have always roamed free at her home.

Alpers said she doesn’t know whether the fire spared her home or not, but she said that as long as her dogs are safe, she doesn’t care about the material things. “I’m kind of worried, but not that much,” she said. “If it’s gone, it’s gone.”

The National Interagency Fire Center said more than 27,000 fires have burned more than 5,800 square miles in the U.S. this year, and in Canada, more than 8,000 square miles (22,800 square kilometers) have burned in more than 3,700 fires so far, according to its National Wildland Fire Situation Report issued Wednesday.