Fast-growing fires throughout California have forced thousands of people to evacuate their homes, with dry winds and high heat whipping up flames and destroying homes.

Officials said they did not yet know how many properties have been lost, but no immediate injuries were reported. It's not clear how any of the blazes began.

In Northern California wine country, authorities ordered 2,000 people to evacuate as a wildfire exploded to more than 39 square kilometres, whipped up by the strong winds that prompted utilities statewide to impose blackouts to prevent such fires from igniting.

An ember wash spreads over the landscape pushed by high winds during the Kincade fire in the Geysers, in Sonoma County, California. (AP)

Embers fly from a tree as the Kincade Fire burns near Geyserville, California. (AP)

The state's largest utility, Pacific Gas & Electric, reported a problem with a transmission tower near where the fire ignited, but it is not clear whether the malfunction sparked the blaze.

Officials ordered an evacuation of the entire community of Geyserville, home to about 900 people and a popular stop for wine country tourists, along with nearby residents. The blaze threatened some of the area's famed wineries and the River Rock Casino as the blaze raged on the outskirts of town.

In Southern California, two fires rolled along the parched foothills north of Los Angeles, forcing at least 40,000 people to flee neighbourhoods where thousands of homes have sprung up in recent decades.

Susi Weaver, the manager of the Hawkeye Ranch in the Mayacamas Mountains above Geyserville, California, sprays down the dry brush as the the Kincade fire delivers firebrands across the property. (AP)

Several homes burned as the blazes fanned by powerful winds swept through dry brush to the edge of communities in the Santa Clarita area. Winds gusting to about 65 km/h pushed the flames, and enormous plumes of smoke were visible for kilometres. People used hoses to try to protect their properties.

Until now, the focus of California's wildfire season had been on power outages that utilities said were necessary to stop high winds over the coming days from toppling power lines and starting fires. But the season kicked into higher gear on Thursday with the arrival of raging fires and the need to quickly escape them.

A series of deadly blazes tore through the same area in Northern California wine country two years ago, killing 44 people.

Photographers documenting the Kincade fire in the Geysers run as the fire approaches Geysers Road in Sonoma County. (AP)

Among those fleeing Geyserville was 81-year-old Harry Bosworth, who awoke before sunrise to find a firetruck and firefighters in his driveway. As he and his wife drove off, flames surrounded their driveway and their barn caught fire.

"I could see the fire coming, so we got the heck out of there," Bosworth said after escaping to his daughter's house in the neighbouring town of Healdsburg.

Julia Jackson of Geyserville-based Jackson Family Wines, which owns more than 40 wine labels and thousands of acres of vineyards, posted on Instagram that her home was "burnt down to the ground."

Firefighters confer while battling the Kincade Fire near Geyserville, California. (AP)

"Stuff is just stuff. Thank God I'm alive," she wrote. Jackson, who founded a climate change conference, said such fires are why she is doing the work.

Another Geyserville evacuee, Isaac Hale, said he woke up to the sound of authorities ordering him out.

"The highway patrol showed up banging on the door, ordering everyone to evacuate because the fire was so close," Hale said, seated on top of his SUV near a road closure checkpoint. "The fire, it just spread so fast."

Flames from the Kincade fire engulf a construction vehicle near Geyserville, California. (AP)

It started on Wednesday night near the Geysers, the world's largest geothermal field, where nearly two dozen power plants draw steam from more than 350 mountain wells to create electricity, California Department Of Forestry And Fire Protection incident commander Mike Parkes said.

It was fuelled overnight by 112 km/h winds in rugged terrain that was hard to reach, he said. Some people were refusing to leave despite the danger, Sonoma County Sheriff Mark Essick said.

"Please heed our evacuation order," he said in a televised news conference. "We really need to be able to fight the fire, rather than worrying about rescuing you."

The fire raged amid rolling blackouts instituted after utility electrical equipment was blamed for setting several blazes in recent years that killed scores of people and burned thousands of homes.

A fire whirl whips across dry brush as the Kincade fire spreads through the region of Sonoma County, California. (AP)

The state's largest electric utility, Pacific Gas & Electric, filed for bankruptcy protection in January as it faced billions of dollars in damages from such wildfires. The investor-owned energy company has set aside billions for insurers and wildfire victims while facing a public backlash over its handling of the outages.

PG&E spokesman Paul Doherty said parts of Geyserville lost power as scheduled Wednesday. The company's outages are affecting half a million people or nearly 180,000 customers.

In Southern California, hot and dry Santa Ana winds led Southern California Edison to cut power to more than 27,000 customers. It was considering additional power cuts to more than 386,000 customers.

The latest outages come two weeks after PG&E shut down power for several days to about two million people.

Flames advance on a Cal Fire dozer transport operator during the Kincade fire in the Geysers, in Sonoma County. (AP)