Wildfire along California's Big Sur forces evacuations

Strong winds pushed a wildfire that broke out in the rugged mountains above Big Sur to the sea, forcing hundreds of residents on this precarious stretch of the California coast to evacuate and authorities to shut its main roadway.

The fire broke out last night in a steep canyon. Fanned by wind gusts of up to 80km/h, it quickly burned at least 6sq km of brush and redwood trees, said Cecile Juliette, a spokeswoman for the California Department of Forestry and Fire Protection.

"The fire lined up with the wind and the terrain and that gave the fire a lot of energy to make a big run," she said today.

The Colorado Fire burns along Highway 1 near Big Sur, California. Photo / AP

Authorities made contact with about 500 residents, urging them to evacuate the sparsely populated area between Carmel and Big Sur. More than 250 firefighters from multiple agencies and volunteer groups, aided by water-dropping aircraft, contained 5% of the blaze.

"The winds have died down and that has worked in our favour," she said.

Authorities shut a stretch of Highway 1 with no estimated time for reopening. The highway along Big Sur is prone to closures due to fire and mudslides from heavy rain that made portions of the roadway collapse to the sea last year and in 2017.

Evacuees shared on social media dramatic images of flames burning behind iconic Bixby Bridge. The tall concrete span has been the backdrop of many car commercials, movies and TV shows, most recently the HBO drama Big Little Lies.

Strong winds were recorded across the San Francisco Bay Area overnight, knocking down trees and power lines and causing outages to at least 18,000 Pacific Gas & Electric customers in the region, the utility said. There were no immediate reports of injuries.

A fallen tree sits on top of a vehicle after strong winds in Upland, California. Photo / AP

In Sonoma County, firefighters extinguished a 2ha fire on Geyser Peak, where gusts above 145km/h were recorded.

The National Weather Service said a similar windy event happened in the region nearly a year ago on the night of January 18. A red flag warning of extreme fire danger was issued then due to the strong winds and much drier conditions.

This time, the region was still moist after December storms dumped heavy snow in the mountains and partially refilled parched reservoirs, providing some relief from what had been an exceptionally dry year.

However, Juliette said the winds quickly dried up vegetation weakened by a prolonged drought and lowered humidity level.

"It's unusual to have fire this size here on the coast at the end of January," she said. "The fact that we had a fire this size is of great concern."

The cause of the fire was under investigation.

Warnings of gusts from 80-113km/h were set to go into effect in much of Southern California by midafternoon today.