Raging wildfire forces 13,000 people to evacuate in northern California

About 13,000 people were ordered to evacuate in northern California as firefighters battle a raging wildfire amid scorching temperatures.

The Thompson fire in Butte county, California, began before noon on Tuesday near the city of Oroville, about an hour outside Sacramento. It quickly grew in size, and had burned through more than 3,000 acres (1,200 hectares) by Wednesday morning. It is uncontained. .

The fire has has damaged vehicles and buildings, according to pictures shared to social media. But the full extent of the damage is unclear.

Oroville officials have declared a local emergency, as the fire spreads towards more populated areas and threatens critical structures, including power lines and a major water supply, CBS reported.

Firefighters responded forcefully to the blaze, which comes amid a scorching heatwave. More than 500 firefighters have been deployed, as well as at least 50 firetrucks and six helicopters, the Butte county fire department said.

The cause of the fire is under investigation.

Related: Brutal California heatwave to coincide with Fourth of July wildfire risks

California’s governor, Gavin Newsom, said on Tuesday that California had secured a fire management assistance grant (FMAG) from the Federal Emergency Management Agency (Fema) to cover some of the costs associated with firefighting.

Earlier in the week, Newsom had activated the state 0perations center to coordinate the response to wildfires and excessive heat across the state.

The blaze comes as California was on high alert for wildfires, with high temperatures and gusty winds exacerbating fire risks.

Starting Wednesday, parts of the state will be subject to “extreme” levels of heat risk – the highest level on the National Weather Service’s index . The extreme conditions could last until Sunday or longer, authorities warned. In some areas, life-threatening triple-digit temperatures could linger for longer than a week.

Temperatures in the state capital, Sacramento, were forecasted to reach between 105F and 115F (40.5C and 46.1C) – conditions that could last until Sunday.

“This is going to be a severe, prolonged, potentially record-breaking heatwave that may have large impacts for much of California ,” said climate scientist Dr Daniel Swain during a broadcast discussion of the heat event on Monday. The long duration will only add to the potential impacts and intensity, especially because little relief can be expected even after the sun sets. “It just isn’t going to cool off – even at night,” Swain said.

The heat was expected to linger through the holiday weekend, and hit inland areas like Sacramento, the San Joaquin valley and the southern deserts the worst.

The torrid conditions were being caused by a ridge of high pressure just off the west coast and a separate ridge that spawned heat warnings and advisories from Kansas and Missouri to the Gulf coast states, according to the National Weather Service. By Tuesday morning, nearly 90 million people across the country were under heat alerts .

Extreme heat is the most deadly type of weather-related disaster, experts say. The dangerous weather conditions this week will pose health risks to large swaths of the population, forecasters cautioned, in particular to people unable to access cooling.

The Associated Press contributed report ing

More on extreme heat and wildfires in the US:

• Brutal heatwave cooks US west during holiday week

• US wildfire season has arrived. Here’s why it could be an explosive summer

• Visualized: the parts of the US where summer heat has risen the most