A 44-year-old man was convicted Friday of pushing his flaming car into a gully after it had gotten stuck, setting off one of California’s largest-ever wildfires.

Judge Kristen Lucena determined after a three-day trial that the man, Ronnie Stout, was guilty of arson for igniting the Park Fire in July 2024, which burned across 429,603 acres in Northern California — about the size of the city of Houston — and destroyed hundreds of homes and other structures.

No one was killed in the blaze, which was the largest ever to be set intentionally in California and the fourth-largest wildfire of any cause, according to the California Department of Forestry and Fire Protection. The fire began near Chico, in Butte County, about 150 miles northeast of San Francisco, and burned for two months across several counties before it was fully contained.

Because Mr. Stout, who lived in Chico, previously was convicted of two serious felonies, robbery and child molestation, he is subject to California’s “three-strikes” law and faces a minimum of 25 years in prison and could be imprisoned for life. His sentencing is set for October.

His lawyer, Nicole Diamond, said in an email that she disagreed with the judge’s verdict, which she said “does not reflect the evidence presented at trial.”

“As I emphasized during the closing argument, while the fire was undeniably a tragedy for the community, the evidence presented at trial did not warrant a conviction” under the arson statute, Ms. Diamond said. That statute says a person is guilty when he “willfully and maliciously” causes a fire.

In a statement, the Butte County District Attorney’s office said that Mr. Stout had been driving back toward Chico in his 2007 Toyota Yaris when he slid off the road and the car got stuck on a raised stretch of dirt. He revved the engine and shifted between forward and reverse, which eventually caused a fire under the car, and then angrily pushed it off the ridge into a gully 60 feet below, prosecutors said.

When an arson investigator called him shortly after the fire began, based on witnesses identifying him, Mr. Stout asked, “What did I do wrong, bro?”

While prosecutors said in their statement that Mr. Stout had intentionally pushed the burning car into the gully, they did not suggest that he had been intent on starting a wildfire.

Ms. Diamond had emphasized at trial that only one witness described seeing Mr. Stout push the car into the gully, according to The Chico Enterprise-Record, and she offered other possibilities for how the car might have rolled to the bottom.

The Park Fire burned six years after the Camp Fire tore through Butte County, leveling the town of Paradise and killing 85 people, becoming by far the deadliest wildfire in California’s history.