A firefighter drinks water in front of a burning house near Oroville, Calif., on Sunday. The first major wildfires after the end of California's five-year drought raged across the state as it was gripped by a record-breaking heatwave. (Josh Edelson/AFP/Getty Images)

Wildfires barreled across the baking landscape of the western United States and Canada, destroying a smattering of homes, forcing thousands to flee and temporarily trapping children and counselors at a California campground.

In California, two major wildfires have sent nearly 8,000 people fleeing to safety.

About 4,000 people evacuated and 7,400 others were told to prepare to leave their homes as fire swept through grassy foothills in the Sierra Nevada, about 60 miles north of Sacramento, the California Department of Forestry and Fire Protection said Sunday.

The fire burned nearly eight square miles, destroyed at least 10 structures and damaged critical infrastructure, leading Gov. Jerry Brown to declare a state of emergency to provide assistance to local authorities.

Fire department spokeswoman Mary Ann Aldrich said more homes were destroyed overnight. An inspection team is trying to determine the extent of the damage.

The area burning was about 10 miles south of Oroville, where spillways in the nation’s tallest dam began crumbling from heavy rain this winter and led to temporary evacuation orders for 200,000 residents downstream.

In Southern California, at least 3,500 people evacuated as two fires exploded in size at separate ends of Santa Barbara County and a third one threatened homes near a town in San Luis Obispo County.

One of the fires grew to 12 square miles, traversing a mountain range and heading south toward coastal Goleta.

There was minimal containment and flames shut down State Route 154, which is expected to remain closed for days. At least 20 structures burned, but officials didn’t say whether they were homes.

Sarah Gustafson, who moved from Washington to California seven months ago, was out running errands when she saw the pillar of smoke rising near her home. She rushed to retrieve her six cats and then spent the night at a Red Cross shelter.

“It was terrifying,” she told the Los Angeles Times. “The sky was orange and black. You could see flames up on the ridge.”

About 90 children and 50 counselors were stuck Saturday at the Circle V Ranch in Santa Barbara and had to take shelter until they could be safely evacuated. Buildings have burned, but officials were not yet sure whether they were homes.

Crews also used aircraft to attack another blaze about 50 miles north that exploded in size to 37½ square miles. About 200 rural homes east of Santa Maria were evacuated when the fire broke out Saturday and was fed by dry gusts.

Some of the firefighters working to contain that blaze were sent to nearby San Luis Obispo County when a fire broke out Sunday and threatened numerous structures near the town of Santa Margarita. Officials said the fire burned at least 200 acres.

In British Columbia, firefighters were contending with more than 200 wildfires that had destroyed dozens of buildings, including several homes and two airport hangars. The three biggest fires, which ranged in size from five to eight square miles, forced thousands of people to flee.

“We are just, in many ways, at the beginning of the worst part of the fire season, and we watch the weather, we watch the wind, and we pray for rain,” Christy Clark, the province’s outgoing premier, told reporters in Kamloops.

Rob Schweizer, manager of the Kamloops Fire Centre, said it had been an unprecedented 24 hours.

“We probably haven’t seen this sort of activity that involves so many residences and people in the history of the province of B.C.,” he said.