The McCabe Fire, which was first reported around 2 a.m. Friday about 10 miles northeast of Geyserville, was 25 percent contained as of 2 p.m. Saturday.
The fire was moving in a northeasterly direction toward Lake County as of this afternoon, Cal Fire Capt. Scott McLean said.
The blaze has prompted the evacuation of at least a dozen homes near a geothermal power plant in the Geysers area along Geysers Road near Cloverdale and Healdsburg, according to Cal Fire.
No injuries have been reported.
The flames destroyed a cooling tower at the power plant on Friday but so far have not reached any other structures, McLean said.
The captain said the fire has been tough to fight due to low humidity and the area's steep terrain and abundance of brush, dry grass and timber.
Gusty winds that have whipped much of the region in recent days have also hindered firefighters' progress, and winds picked up in the Geysers area again this morning, McLean said.
"Basically you have everything you don't want to have," he said. "It's making it very difficult, especially to access the fire."
This afternoon, crews continued to attack the flames and attempt to contain the fire.
A total of 783 fire personnel from more than a dozen agencies have been called to fight the wildfire since Friday morning, according to Cal Fire.