California wildfires chewed through rural areas north of Los Angeles and east of San Diego on Thursday, racing through bone-dry brush and prompting evacuations as the state sweltered under a heat wave that could last through Labor Day.

The Route Fire near Castaic in northwestern Los Angeles County raged through more than 8 square miles of hills containing scattered houses. Traffic was snarled on Interstate 5, a major north-south route running through fire area. Containment was estimated at 12%.

Aircraft drew water from nearby Castaic Lake to dump on the flames. There were no immediate reports of damage to buildings but a mobile home park with 94 residences was evacuated.

An elementary school also was evacuated. Temperatures in the area on Wednesday hit 107 degrees (42 Celsius) and winds gusted to 17 mph, forecasters said.

Temperatures in much of California were so high that Gov. Gavin Newsom declared a state of emergency and the state power grid operator asked residents to voluntarily reduce use of electricity.

Eight firefighters were treated for heat-related problems, including six who were sent to hospitals, but all were in good condition, Los Angeles County Fire Department Deputy Chief Thomas Ewald said.

More injuries were expected as crews cope with extreme heat that was expected to stretch into next week, Ewald said during a news conference Wednesday night.

“Wearing heavy firefighting gear, carrying packs, dragging hose, swinging tools, the folks out there are just taking a beating,” he said.

Another fire burned at least four buildings, including a home, and prompted evacuations in the Dulzura area in eastern San Diego County near the U.S.-Mexico border. It swiftly grew to more than 6 square miles and prompted evacuation orders for at least 400 homes, authorities said.

The fire was 5% contained, but firefighters warned that weather would continue to be a challenge.

Two state highways were closed. The Mountain Empire Unified School District also shut down.

U.S. Customs and Border Protection announced that the Tecate port of entry with Mexico closed three hours early on Wednesday night because of the fire and wouldn’t reopen until conditions improved to ensure “the safety of the traveling public.” Travelers could continue to use the 24-hour Otay Mesa crossing.

No injuries were immediately reported, but there were “multiple close calls” as residents rushed to flee, said Capt. Thomas Shoots with the California Department of Forestry and Fire Protection.

“We had multiple 911 calls from folks unable to evacuate” because their homes were surrounded by the fire, Shoots told the San Diego Union-Tribune.

Wildfires have sprung up this summer throughout the Western states. The largest and deadliest blaze in California so far this year erupted in July in Siskyou County. It killed four people and destroyed much of the small community of Klamath River.

Scientists have said climate change has made the West warmer and drier over the last three decades and will continue to make weather more extreme and wildfires more frequent and destructive.