The fire started at about 6:30 a.m.in Butte County, which is about 85 miles north of Sacramento, officials from the California Department of Forestry and Fire Prevention said at a press conference Thursday.
A local fire official said there were multiple injuries among civilians and firefighters.
The blaze by Thursday morning had already charred 18,000 acres, forcing the evacuation of the 27,000 residents of Paradise, about 150 miles northeast of San Francisco, and other communities, Cal Fire said in a statement. Smoke from the fire could be seen from the scene of the mass shooting at a Thousand Oaks bar that left 12 people dead. He started putting out the fire and yelled at her to get back inside, she says. "Due to the fluid and rapidly changing conditions, residents are urged to stay updated through official sources for changes to evacuations and road closures", said a CalFire incident report Thursday night.
Acting California Gov. Gavin Newsom declared a state of emergency in the area and requested a federal emergency declaration, saying that high winds and dry brush presented ongoing danger.
Fortune will continue to update this post as California's 2018 fires continue to rage.
With a blaze in Butte County reddening the Berkeley skies and a fire in Oakland prompting full response from its fire department, Berkeley Fire Department is sending engines for support.
"It was absolutely dark", said resident Mike Molloy, who said he made a split decision based on the wind to leave Thursday morning, packing only the minimum and joining a sea of other vehicles.
TV personality Adrienne Janic said on Twitter that firefighters were using her home as a command centre.
"I'm on the phone crying, talking to my husband, just hoping I can get out of there", she said.
Authorities fear the fire, fueled by strong winds, could reach Chico - a city of 90,000 people where many Butte County families already have evacuated to shelters.
The wildfire was reported around daybreak.
According to Sacramento Bee reporter Ryan Lillis, some 60 to 70 people were awaiting an emergency evacuation at a Walgreen's in Paradise.
A red flag warning is Cal Fire's most serious caution.
The Adventist Health Feather River Hospital in Paradise evacuated all its patients and staff, given its close proximity to the fire, and transported them safely to hospitals in neighboring towns, said Jill Kinney, an Adventist Health spokeswoman. "We tried to get all the nondigital things that we could - you know, stuff that couldn't be replaced", Peete said. Within six hours, it had grown to more than 69 square kilometres, Gaddie said. 'There are dozens of strike teams that we're bringing in from all parts of the state'.
Four of the hospital's employees were briefly trapped in the basement and rescued by California Highway Patrol officers, Kinney said.
A Red Flag Warning is in place through Friday morning in the Butte County area, and winds are expected to gust at speeds as high as 40 miles per hour overnight, according to the National Weathers Service.