Wildfires barrelled across the baking landscape of the western US and Canada, destroying a smattering of homes, forcing thousands to flee and temporarily trapping children and counsellors at a California campground.

On Sunday, firefighters were contending with more than 200 wildfires burning in British Columbia that destroyed dozens of buildings, including several homes and two airport hangars.

The three biggest fires, which ranged in size from 14 to 20 square kilometres, had forced thousands of people to flee.

A combination of high temperatures and parched land has added to the difficulties of firefighters in California, which is regularly hit by wildfires at this time of year.

A look Friday evening as firefighters work on the #Alamofire in California - Video: @EliasonMike & the Santa Barbara County Fire Dept #CAwx pic.twitter.com/ZKz8zTLBL6 — WeatherNation (@WeatherNation) July 8, 2017

In Northern California, a Butte County wildfire swept through grassy foothills and destroyed 10 structures, including homes, and led to several minor injuries.

Burned-out pickup trucks were left in ashes, surrounded by charred, leafless trees. The metal frame of a mobile home and a vintage stove were left standing in scorched debris at one site.

The blaze about 100km north of Sacramento grew rapidly to more than 18sq km and was nearly 20 percent contained, according to the California Department of Forestry and Fire Protection.

Southern California crews hope slightly cooler temperatures and diminishing winds will help in the battle on Sunday against major wildfires that have destroyed structures, closed a highway and forced evacuations.

One of two fires raging in Santa Barbara County grew to 31sq km, traversing a mountain range and heading south toward coastal Goleta.

"The plan is to hit it with air tankers to keep it from moving to the south and to the east," said county fire captain Dave Zaniboni. "There's less heat and less wind, which makes things a little easier."

Crews were also using an air attack against another blaze about 80km north that exploded in size to 97sq km.

About 200 rural homes east of Santa Maria were evacuated after the fire broke out Saturday and was fed by dry gusts.