LOS ANGELES — Tens of thousands of people in northern California have been told to leave their homes as wildfires grow across the state during a heatwave.

About 28,000 people were under evacuation warnings or orders on Thursday after the Thompson fire broke out two days earlier, according to the California Department of Forestry and Fire Protection (CalFire).

Dangerously hot weather is expected to continue with temperatures of 118F (47C) forecast in some areas until early next week.

No one has died, while 74 structures across the state have been destroyed or damaged from fires this season.

The city of Oroville, near where the Thompson fire started, canceled its 4 July Independence Day fireworks celebration over the risk of starting another blaze.

“The last thing we need is somebody who’s purchased fireworks from a local fire stand going out and doing something stupid,” Butte County Sheriff Kory Honea said. “Don’t be an idiot, cause a fire and create more problems for us.”

Honea said the area had seen four fires within the last couple of weeks and cautioned that danger was far from over.

“This is a bad fire season," he added.

As of Thursday evening, the Thompson Fire was 7% contained, indicating a little bit of progress as a crew of nearly 2,000 battles the flames.

At least four people have been injured, according to CalFire,1 though the extent of their injuries is unknown.

Fire season started recently in California and usually runs until October. The size and intensity of fires in the state have grown in recent years.

The amount of burned areas in the summer in northern and central California increased five times from 1996 to 2021 compared to the 24-year period before, which scientists attributed to human-caused climate change.

This week, the National Weather Service issued excessive heat and red flag warnings — indicating hot, dry and windy weather — across the state. The agency said “dangerous” temperatures posed a major to extreme risk of heat stress or illnesses.

According to CalFire, around two dozen fires have burned more than 10 acres sparked across the state since the last week of June. The largest one, at nearly 14,000 acres, was in Fresno county.

California Governor Gavin Newsom declared a state of emergency in Butte County to provide resources.

The Thompson fire started in Oroville, about 70 miles north of the state capital Sacramento, on Tuesday. The city is around 20 miles from Paradise, which was devastated by the Camp Fire in 2018 that killed 85 people. Fires hit the region again in the years following.

CalFire spokesman Robert Foxworthy told the BBC that the fire was no longer growing amid lighter wind speeds, but the heat — which was predicted to hit 110F (43C) on Thursday — was the "biggest factor" impacting firefighters.

Two days after the fire broke out, many residents remained unable to return home.

Brittanie Hardie, a Louisiana native and recent California transplant, told the San Francisco Chronicle that she had not been at home when her girlfriend evacuated their flat, and had nothing but the clothes she was wearing.

"I knew wildfires were bad in California, but I didn't know it was this bad," Hardie told the newspaper.

Oroville City Council member Shawn Webber posted a video on Facebook on Wednesday showing hillsides smoking on both sides of a road, but thanked firefighters for preventing further destruction.

California's state parks system said agencies responding to the fire “also have employees with families displaced by these evacuations who are tirelessly assisting the community of Lake Oroville”. — BBC