Firefighters lined roads to keep flames from reaching homes as helicopters dropped water on a growing wildfire on Wednesday.

The wildfire in Northern California has forced at least 13,000 people to evacuate and another day of extreme heat is expected to come.

The Thompson fire broke out before noon Tuesday about 70 miles (110km) north of Sacramento, in and around the city of Oroville, in Butte County.

It sent up a huge plume of smoke and grew to nearly 4.7 square miles (12.1 square kilometres) by Wednesday morning. It was 0% contained.

The city of about 20,000 people declared a state of emergency on Tuesday night and several homes have been destroyed, KCRA-TV reported.

There was no word of injuries as two evacuation centres were set up in Butte County.

More high temperatures above 100F (37.8C) were forecast for Wednesday, the National Weather Service said.

On Tuesday, the governor’s office announced that federal funding had been approved to help with firefighting efforts.