Crews battling a wind-stoked blaze in Northern California used cooler temperatures early Thursday to clear brush and expand containment lines using bulldozers and hand tools.
They also got help from the fire itself, as its northern flank continued to merge with another massive blaze that was nearly fully contained, said California Department of Forestry and Fire Protection spokesman Daniel Berlant.
"That stopped the fire from spreading any further," he said.
The fire in Lake and Napa counties was 33 percent contained, up from 16 percent the previous day. It had burned through 37 square miles and was still threatening 50 structures, most of those homes.
At least 150 people have evacuated their homes since Sunday. Some in the region about 100 miles north of San Francisco had only recently returned after fleeing an earlier blaze.
About 2,000 firefighters took a stand against the flames Wednesday, some of them lighting backfires along a road as plumes of black and white smoke rose into the sky.
Most had been reassigned from a massive fire nearby that charred 109 square miles, but was 95 percent contained after destroying 43 homes.
The fire began in dry timber and brush Sunday several miles from the community of Lower Lake. It leapt from Lake County into Napa County, but no vineyards were threatened in the famous wine-growing region.
Empire Mini Storage manager Desiree Mcalear said the business in Middletown has had numerous calls and visits from people who want to rent units in case they have to evacuate.
"They're absolutely scared and terrified," she said. "If the winds decide to blow this way, then we all need to take action. Right now, we have the luxury of waiting and being patient."
The causes of the fires remain under investigation.
Temperatures have been relatively mild, but the gusty winds and dry conditions have stoked the flames.