A fast-moving fire in Northern California is threatening hundreds of homes as authorities ordered at least 5000 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 to 200 hectares in about an hour, the Siskiyou Sheriff's Office said in a statement on Friday.
In Southern California, firefighters were making progress against two big wildfires despite dangerously hot weather.
They 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 18 square kilometres and containment increased to 20 per cent.
More than 1500 people had to evacuate the area near the US-Mexico border when the fire erupted on Wednesday. All evacuations were lifted by Friday afternoon.
Two people were taken to hospital 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.