California's largest wildfire explodes in size

More than 130 structures have been destroyed by this fire and thousands more are threatened as evacuations were ordered in four counties.

It stood about 1250 square kilometres on Friday and was moving quickly north and east after igniting on Wednesday when authorities said a man pushed a burning car into a gully in Chico and then calmly blended in with others fleeing the scene.

"There's a tremendous amount of fuel out there and it's going to continue with this rapid pace," Cal Fire incident commander Billy See said.

The Park Fire on Friday was one of more than 110 active blazes in the US. (AP PHOTO)

The fire was advancing up to 20 sq km an hour on Friday, he said.

Communities elsewhere in the US west and Canada were under siege from a fast-moving blaze sparked by lightning, which sent people fleeing on fire-ringed roads in rural Idaho to a new blaze that was causing evacuations in eastern Washington.

In eastern Oregon, a pilot was found dead in a small air tanker plane that crashed while fighting one of the many wildfires spreading across several Western states.

More than 110 active fires covering more than 7250 sq km were burning in the US on Friday, according to the National Interagency Fire Centre.

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.

The most damage has been to the Canadian Rockies' Jasper National Park, where a fast-moving wildfire forced 25,000 people to flee and devastated the park's namesake town, a World Heritage site.

Oregon has the biggest active blaze in the United States, the Durkee Fire, which combined with the Cow Fire to burn nearly 630 square miles.

It remains unpredictable and was only 20 per cent contained on Friday, according to the government website InciWeb.