By Alex Dobuzinskis

LOS ANGELES (Reuters) - A Southern California wildfire raged unchecked in thick brush on Wednesday after destroying dozens of houses near a highway corridor between Los Angeles and Las Vegas and forcing as many as 80,000 residents to flee their homes, officials said.

The so-called Blue Cut Fire ignited on Tuesday in the mountainous Cajon Pass and quickly ballooned to 30,000 acres (12,140 hectares), putting firefighters on the defensive.

Fire officials described the blaze as unusually fierce, even for a year of intense wildfires in the U.S. West, where years of drought have dried trees and brush and placed a heavy burden on firefighting resources.

"In my 40 years of fighting fire, I've never seen fire behavior so extreme as it was yesterday," Michael Wakoski, the incident commander on the fire, said on Wednesday at a news conference.

As many as eight wildland fires were burning in California on Wednesday, three of them scorching thousands of acres as firefighters sought help from emergency responders from other states and the California National Guard.

Given the dryness and ongoing warm weather, U.S. government forecasters have said Southern California faces a potential threat from major wildfires until December.

Santa Ana winds, which sweep desert air to California's coast while driving the fires, are due to kick up next month, California Department of Forestry and Fire Protection (Cal-Fire) spokeswoman Lynne Tolmachoff said by phone. September and October are often the peak of the state's wildfire season.

The Blue Cut Fire, named for a narrow gorge north of San Bernardino where it started, was zero percent contained as it threatened the town of Wrightwood near a ski resort and other communities in a partly rural area, authorities said.

The cause of the fire is under investigation.

Authorities said they were forced to close part of Interstate 15, which runs through the Cajon Pass between Las Vegas and the Los Angeles area, and to order about 80,000 residents to evacuate.

Thick columns of smoke blocked out the sky above mountain peaks as the fire overran a number of properties, leaving behind barren lots with blackened appliances and vehicles stripped of nearly everything but metal.

Louis Penna, a spokesman for the San Bernardino County Fire Department, said in an email an official damage estimate was not available but that dozens of destroyed structures were clearly visible.

"There will be a lot of families that come home to nothing," San Bernardino County Fire Chief Mark Hartwig told reporters.

The Los Angeles Times reported hundreds of residents of Wrightwood were staying in their houses, despite dire warnings from authorities.

"It's to the point where explosive fire growth is the new normal this year," Glenn Barley, a fire chief with the San Bernardino unit of Cal-Fire, told reporters.

About 600 miles (970 km) to the northwest, the Clayton Fire, named for a creek near where it broke out, was 40 percent contained after charring 4,000 acres in and around the community of Lower Lake and destroying 175 homes and businesses.

That fire destroyed a 150-year-old Methodist church in the community of Clearlake, according to the Los Angeles Times.

The Chimney Fire, named for its starting point near Chimney Rock Road on San Luis Obispo County, destroyed 40 structures and burned 7,300 acres by Wednesday afternoon, and was 25 percent contained.

As of Aug. 12, California had spent $164 million to combat wildfires this year, Tolmachoff said. That was before the Blue Cut, Clayton or Chimney fires had broken out.

(Reporting by Alex Dobuzinskis in Los Angeles and Sharon Bernstein in Sacramento, Calif.; Editing by Alistair Bell and Matthew Lewis)