WEED, Calif. (AP) — A fast-moving fire in Northern California threatened hundreds of homes Friday and authorities ordered at least 5,000 residents across three communities to leave immediately.

Residents of the towns of Weed, Lake Shastina and Edgewood in Siskiyou County were told to evacuate after the blaze spread in hot and windy conditions to 500 acres in about an hour, the Siskiyou Sheriff’s Office said in a statement.

Photos posted on social media showed massive flames in the town of Weed, about 70 miles north of the city of Redding.

Christopher Rock, an employee at the Mayten Store in Montague, a town 30 miles (48 kilometers) north of Weed, said evacuees from the fire had swarmed the pumps.

“It’s really busy right now,” he said. “You can’t see the flames from here, just a lot of smoke.”

Marco Noriega, brewmaster at Mount Shasta Brewing Company, said they received the notice to evacuate about an hour ago and he sent the 10 customers and three employees away. He said the power is out and they have received little information.

Smoke is to the north and winds are blowing from the south, keeping the fire away. He sounded calm as he cleaned up.

“I’ve been through it before, so long as the wind stays in the direction it is, I’m all right. But I know the wind switches quickly,” he said by phone.

The National Weather Service issued a red flag warning for Siskiyou County from 11 a.m. to 11 p.m. Friday. Winds were expected to reach up to 31 mph in the Weed area, the weather service said.

In Southern California, firefighters were making progress Friday against two big wildfires despite dangerously hot weather.

Containment of the Route Fire along Interstate 5 north of Los Angeles increased to 37% and it remained at just over 8 square miles (21 square kilometers) in size, a California Department of Forestry and Fire Protection statement said.

Firefighters were focusing on mopping up hotspots and building more containment lines, trying to get most of the hard work done before the midday heat, Cal Fire said.

California is in the grip of a prolonged heat wave. Temperatures have been so high that residents have been asked for three consecutive days to conserve power during late afternoon and evening hours when solar energy declines.

On Wednesday, seven firefighters working the Route Fire in triple-digit temperatures had to be taken to hospitals for treatment of heat illnesses. All were released.

“Excessive heat, low humidity and steep terrain will continue to pose the biggest challenge for firefighters,” Cal Fire said.

The tally of destroyed structures remained at two, and all evacuation orders were lifted.

In eastern San Diego County, the Border 32 Fire remained at just under 7 square miles (18 square kilometers) and containment increased to 20%.

More than 1,500 people had to evacuate the area near the U.S.-Mexico border when the fire erupted Wednesday. All evacuations were lifted by Friday afternoon.

Two people were hospitalized with burns. Three homes and seven other buildings were destroyed.

Scientists say 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.