The Ventura County Fire Department said over 27,000 people had been told to evacuate their homes and the fast-moving fire in the coastal county north of Los Angeles had grown to 31,000 acres (12,545 hectares).
"The prospects for containment are not good," Ventura County Fire Chief Mark Lorenzen told a late night news conference. "Really, Mother Nature is going to decide when we have the ability to put it out."
The National Weather Service said easterly Santa Ana winds fuelling the fire had registered gusts of up to 50 miles per hour (80 kilometres per hour).
"The fire is pushing quickly towards the city of Ventura," Mr Lorenzen said, and has reached the eastern city limits. The Pacific Ocean beachfront city has a population of around 100,000.
The fire chief said one death had been reported. "As the individual was evacuating from the fire, the car overturned," he said.
The Southern California Edison utility company said 180,000 customers in Ventura County and 83,000 in Santa Barbara County were without power.
Ventura County officials said about 500 firefighters were currently battling the blaze, known as the Thomas Fire, and more were being deployed.
"Fixed wing aircraft and helicopters are expected to attack the fire at daybreak," the Ventura County website said.
Mr Lorenzen said the fire was consuming dry brush.
"It's heavy brush, brush that hasn't burned in 15 to 20 years," he said.
"And it's been a five/six-year drought so the fuel is just tinder dry and just as ripe as can be for fire spread."
This has been California's deadliest year ever for wildfires. More than 40 people died in the state's wine-producing country in fires in October.
