LOWER LAKE, Calif. — Erratic winds Wednesday fanned a wildfire burning through rugged hills in Northern California that has driven people from their homes and pushed the flames across two counties.

At least 150 people have evacuated their homes since Sunday. Many in the region about 100 miles north of San Francisco had only recently returned after fleeing an earlier blaze.

Crews lit backfires Wednesday along a road elsewhere in the region as plumes of black and white smoke rose into the sky.

The fire had expanded across 32 square miles and crews had the flames just 16 percent contained, the California Department of Forestry and Fire Protection said. Full containment wasn’t expected until Monday.

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.