As of Thursday evening, the fire had consumed nearly 150,000 acres  an area more than two-fifths the size of the city of Los Angeles  and had become the largest in the county’s history. The fire has been fueled in large part by a mix of dry brush, record heat, and steep slopes that have slowed firefighters.

Still, the fire is considered particularly unusual because it has spread so quickly without the help of the ferocious Santa Ana winds, which typically drive Southern California’s wildfires. The Angeles National Forest is usually struck by about 200 fires every year, most of which are quickly controlled.

Peak fire season in Southern California begins in the fall, when the Santa Ana winds flare up. As a result fire officials have said the state could be in for a particularly long and harsh wildfire season this year.

Earlier in the day, Gov. Arnold Schwarzenegger told reporters that crews were making progress against the flames, containing about 40 percent of the Station Fire, but he cautioned that it was still far from over. Fire officials have said it could be another two weeks before the blaze is completely contained.

Mr. Schwarzenegger toured the fire-ravaged Vogel Flats area of the Angeles National Forest and later thanked firefighters for all of their work in putting out the flames. At one point on the tour, Mr. Schwarzenegger, a former bodybuilder, picked up a 30-pound dumbbell found in rubble. “Even though we are still battling those fires, we are now trying to help get people’s lives rebuilt,” he said.