Hundreds of fires were burning across California, including 23 major fires or groups of fires that governor Gavin Newsom blamed on “extraordinary weather” and “all of these lightning strikes”.
He said the state has recorded nearly 11,000 lightning strikes in 72 hours and knows of 367 fires.
In central California, a pilot died after crashing his helicopter about an hour from New Coalinga Municipal Airport while dropping water in western Fresno County.
The pilot, whose name has not been released, was working with Guardian Helicopters, based in Fillmore, which had a contract with CalFire to provide emergency services as needed, officials said.
Up to seven people were injured in a fire in Stanislaus County, south-east of San Francisco, Sheriff Jeff Dirkse told the Sacramento Bee.
One had major burn injuries and all were taken by ambulance for treatment, he said.
Two fires in Solano County prompted evacuation orders for 8,000 residents near the Russian River. In Healdsburg, with a population of about 12,000, people were warned late on Wednesday to be ready to flee.
Ash and smoke filled the air in San Francisco, which is surrounded by wildfires to the north, east and south.
The LNU Lightning Complex is made up of several fires in five counties north of San Francisco, including in Vacaville, a city of about 100,000 people between San Francisco and Sacramento.
Nearby Travis Air Force Base ordered non-mission essential personnel to evacuate.
The fire had consumed nearly 194 square miles (502 square kilometres) by Wednesday night, an area larger than the size of San Jose.
It jumped the Interstate 80 motorway on Wednesday afternoon, briefly blocking traffic in both directions.
Several thousand people in the small communities of Angwin and Deer Park were ordered to evacuate.
Police and firefighters warned residents before dawn to evacuate as flames encroached on Vacaville. At least 50 structures were destroyed, including some homes, and 50 were damaged.
In eastern San Francisco Bay, a cluster of 20 separate lightning-sparked fires called the SCU Lightning complex was threatening about 1,400 structures in rugged terrain with dense brush. The fires have torched 133 square miles (344 square kilometres).
To the south of San Francisco in San Mateo and Santa Cruz counties, about 22,000 people were ordered to evacuate because of a fire in dense wooded parkland, fire department spokesman Jonathan Cox said.
At least 20 homes had burned, fire officials said.
About 22 fires are part of the complex and most were in relatively remote, dense brush until strong winds overnight on Tuesday pushed them into more populated areas, merging some of the fires together.
The cluster of wine country fires threaten an area that only last year grappled with another massive blaze that forced 200,000 to flee – a task made more complicated this year because of the pandemic.
“This is an incredibly emotional and stressful time for most of us who’ve endured a number of wildfires over the last few years,” said Sonoma County Sheriff Mark Essick.
South of Carmel, nearly 50 miles of the scenic Highway 1 along the coast was closed due to fires.
In Southern California, an eight-day-old blaze grew to nearly 50 square miles (106 square kilometers) near Lake Hughes in the northern Los Angeles County mountains.
Chewing through century-old fir, oak and pine, the fire continued to be a threat to 4,570 structures after destroying a dozen.
Dangerously hot weather and rough terrain challenged firefighters’ efforts to increase containment, currently estimated at 36%.
