Firefighters light backfires as they try to contain the Thomas wildfire which continues to burn in Ojai, California, on December 9, 2017.

The army of firefighters, heavy equipment and aircraft battling what has become the third-largest wildfire in California history faced a forecast of extreme fire danger caused by high winds and dry conditions this weekend.

The Thomas Fire has burned more than 400 square miles northwest of Los Angeles and is only 35 percent contained. Forecasters expect strong Santa Ana winds this weekend to whip the flames with gusts up to 40 mph. No rain is forecast, and the National Weather Service reported the area is enduring its second-driest water season on record.

As of Saturday morning, the Thomas Fire had burned 259,000 acres, with the potential to become the biggest single fire in California history. The current record is held by the 2003 Cedar Fire, which killed 15 people and burned just over 273,000 acres in San Diego.

The Thomas Fire is burning in Ventura and Santa Barbara counties and threatening mansions in Montecito. Photos posted to social media Saturday morning showed a smoke column towering over the area, driven by the high winds. Television host Ellen DeGeneres on Thursday night tweeted a photo thanking firefighters after she and her wife evacuated the area. The fire has burned more than 1,000 buildings, including well over 750 homes, authorities said.

As of Saturday morning, about 8,300 firefighters, 29 helicopters and 77 bulldozers were working the fire. Two people have been killed in the blaze. Firefighter Cory Iverson, 32, died Thursday, but authorities have not yet released the circumstances of his death. Virginia Pesola, 70, of Santa Paula, died in a car crash earlier this month while evacuating.