Thousands of firefighters battling an unruly Northern California wildfire were aided overnight by cooler temperatures and higher humidity.

But the fire is still less than a quarter contained.

Firefighting officials said crews made progress Tuesday with some help from light rain. The blaze has charred 106 square miles (275 square kilometers) and it isn't expected to be completely contained until at least Monday. Crews hope the weather will cooperate Wednesday.

"It's going to be a little bit hotter and a little bit dryer, and the winds are just going to blow a little bit more but it's not going to be crazy," California Department of Forestry spokesman Mike Yeun said Wednesday morning. "We are just going to hope for the best."

More than 3,000 firefighters are battling the smoky blaze.

"The guys on the line have been incredible and did really good work (Tuesday night). We are going to try to hold this and hopefully it will not take off," Yeun said.

The fire is burning about 110 miles north (160 kilometers) of San Francisco along rugged, parched terrain in Lake, Yolo and Colusa counties.

The cause of the fire is under investigation. Since it started last Wednesday, more than 13,000 people were required or urged to leave their homes, vacation cabins and campsites.

Teams on Tuesday were able to build a buffer between the flames and some of the estimated 6,900 homes it threatens. Despite the fire's growth, no additional homes were consumed outside the two dozen already destroyed.

The fire is by far the largest of 11 burning in Northern California

The National Interagency Fire Center in Boise, Idaho, has the wildfire listed as the nation's highest priority for crews and equipment, spokesman Mike Ferris said.

He called the fire "one big monster."

Crews have conducted controlled burns, setting fire to shrubs to rob the blaze of fuel and protect homes in a rural area of grasslands and steep hills.

President Barack Obama was briefed on the fire and has asked his aides to stay in close touch with California Gov. Jerry Brown and other local officials, the White House said.


Kristin J. Bender reported from San Francisco. Associated Press writer Lisa Leff in San Francisco contributed to this report.