The Park Fire had scorched more than 1430 square kilometres of northern California as of Sunday morning, darkening the sky with smoke and haze and contributing to poor air quality in a large swathe of the northwestern US and western Canada.
Although the sprawling blaze was only 12 per cent contained, cooler temperatures and increased humidity could help crews battle the fire, which has drawn comparisons to the 2018 Camp Fire that tore through the nearby community of Paradise, killing 85 people and torching 11,000 homes.
First responders initially focused on saving lives and property endangered by the Park Fire but that had shifted to confronting the blaze head on, a Park Fire headquarters spokesman said.
About 3400 firefighters, aided by numerous helicopters and air tankers, are battling the blaze, which started on Wednesday.
About 3400 firefighters, aided by numerous helicopters and air tankers, are battling the Park Fire. (AP PHOTO)
"This fire is surprising a lot of people with its explosive growth," he said. "It is kind of unparalleled."
The fire had destroyed at least 66 structures and damaged five others, Tracy said.
Authorities initially believed 134 structures had been lost, based on drone footage, but they lowered the number after teams assessed the damage in-person.
"Unfortunately, that number will probably go up," Tracy said.
The Park Fire started on Wednesday, when authorities say a man pushed a burning car into a gully in Chico and then fled.
A Chico man was arrested on Thursday and is due in court on Monday.
The Park Fire was one of more than 100 blazes burning in the US on Sunday, according to the National Interagency Fire Center.
Some were sparked by the weather, with climate change increasing the frequency of lightning strikes as the western US endures blistering heat and bone-dry conditions.
In southern California, a fire in the Sequoia National Forest swept through the community of Havilah after burning 124 sq km in less than three days.
Fires were also burning across eastern Oregon and eastern Idaho.
