US authorities have announced the death of a pilot of a helicopter fighting fires in California.
The pilot was the only person on board the water-dropping helicopter, which crashed near the city of Coalinga.
California Governor, Gavin Newsom, has declared a state of emergency as authorities battle hundreds of blazes.
Several people have fled their homes in areas near San Francisco after several quick-moving wildfires swept into the region.
The city of Vacaville is the most at risk. It is home to about 100,000, which lies between San Francisco and Sacramento.
Officials made frantic effort to clear homes.
According to fire officials, 50 structures have burned down in Vacaville, with another 50 damaged by the fire.
“We are experiencing fires the likes of which we haven’t seen in many, many years,” Governor Newsom told reporters.
The blazes are thought to have been sparked by a heatwave combined with nearly 11,000 lightning strikes which have hit the state over the last three days.
Earlier this week, one of the highest ever temperatures on Earth was recorded in California’s Death Valley.
Across the US western states on Wednesday, nearly 45 million people were living in areas under some form of excessive heat warning or heat advisory.
Mr Newsom said 367 known fires have been recorded so far, but noted that “the prospect of that going up is very real”.
“As those lightning strikes spark, as you have a lot of smoke, you have a difficult time determining total number of fires until certain things clear and we have the opportunity to go to more remote parts of the state,” he added.
So far this year the US has experienced fewer wildfires than in 2019.