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Firefighters battle flames, terrain in hard-to-reach wildfire north of Los Angeles

  • The Grand fire releases a large plume of smoke as it burns more than 3,000 acres of wildlands near Frazier Park on Wednesday, May 15, 2013.Cooler temperatures and lighter winds are helping hundreds of firefighters combat a 3,000-acre wildfire. (AP Photo/Los Angeles Times, Luis Sinco) OUTS; ORANGE COUNTY REGISTER, LA DAILY NEWS, VENTURA COUNTY STAR, INLAND VALLEY DAILY BULLETIN, LA OPINION), SOMETIMES: -CALON (LONG BEACH PRESS-TELEGRAM) NO FORNS, NO SALES, MAGS OUT, MANDATORY CREDIT

    The Grand fire releases a large plume of smoke as it burns more than 3,000 acres of wildlands near Frazier Park on Wednesday, May 15, 2013.Cooler temperatures and lighter winds are helping hundreds of firefighters combat a 3,000-acre wildfire. (AP Photo/Los Angeles Times, Luis Sinco) OUTS; ORANGE COUNTY REGISTER, LA DAILY NEWS, VENTURA COUNTY STAR, INLAND VALLEY DAILY BULLETIN, LA OPINION), SOMETIMES: -CALON (LONG BEACH PRESS-TELEGRAM) NO FORNS, NO SALES, MAGS OUT, MANDATORY CREDIT  (The Associated Press)

  • A firefightier watches a backfire set in Hungry Valley State Park to halt the prgress of the Grand fire, which charred more than 3,000 acres of wildlands near Frazier Park on Wednesday, May 15, 2013. Cooler temperatures and lighter winds are helping hundreds of firefighters combat a 3,000-acre wildfire. (AP Photo/Los Angeles Times, Luis Sinco) OUTS; ORANGE COUNTY REGISTER, LA DAILY NEWS, VENTURA COUNTY STAR, INLAND VALLEY DAILY BULLETIN, LA OPINION), SOMETIMES: -CALON (LONG BEACH PRESS-TELEGRAM) NO FORNS, NO SALES, MAGS OUT, MANDATORY CREDIT

    A firefightier watches a backfire set in Hungry Valley State Park to halt the prgress of the Grand fire, which charred more than 3,000 acres of wildlands near Frazier Park on Wednesday, May 15, 2013. Cooler temperatures and lighter winds are helping hundreds of firefighters combat a 3,000-acre wildfire. (AP Photo/Los Angeles Times, Luis Sinco) OUTS; ORANGE COUNTY REGISTER, LA DAILY NEWS, VENTURA COUNTY STAR, INLAND VALLEY DAILY BULLETIN, LA OPINION), SOMETIMES: -CALON (LONG BEACH PRESS-TELEGRAM) NO FORNS, NO SALES, MAGS OUT, MANDATORY CREDIT  (The Associated Press)

  • The Grand fire burns into the Los Padres National Forest near Gorman, Calif., where the  blaze charred more than 3,000 acres of wild lands on Wednesday, May 15, 2013. Wednesday, May 15, 2013. Cooler temperatures and lighter winds are helping hundreds of firefighters combat a 3,000-acre wildfire. (AP Photo/Los Angeles Times, Luis Sinco) OUTS; ORANGE COUNTY REGISTER, LA DAILY NEWS, VENTURA COUNTY STAR, INLAND VALLEY DAILY BULLETIN, LA OPINION), SOMETIMES: -CALON (LONG BEACH PRESS-TELEGRAM) NO FORNS, NO SALES, MAGS OUT, MANDATORY CREDIT

    The Grand fire burns into the Los Padres National Forest near Gorman, Calif., where the blaze charred more than 3,000 acres of wild lands on Wednesday, May 15, 2013. Wednesday, May 15, 2013. Cooler temperatures and lighter winds are helping hundreds of firefighters combat a 3,000-acre wildfire. (AP Photo/Los Angeles Times, Luis Sinco) OUTS; ORANGE COUNTY REGISTER, LA DAILY NEWS, VENTURA COUNTY STAR, INLAND VALLEY DAILY BULLETIN, LA OPINION), SOMETIMES: -CALON (LONG BEACH PRESS-TELEGRAM) NO FORNS, NO SALES, MAGS OUT, MANDATORY CREDIT  (The Associated Press)

Firefighters had to battle terrain as much as flames as they worked to surround a wildfire entering its third day in harsh hills and mountains north of Los Angeles.

Temperatures dipped Thursday and were expected to remain cool on Friday, but winds upwards of 20 mph continued to swirl, and much of the blaze that has blackened some 3,800 acres was in rocky, rugged, difficult-to-reach places, making containment a challenge.

After a heavy aerial effort Thursday, the fire was 25 percent contained by nightfall.

The fire broke out near Interstate 5 when temperatures were in the 80s, and though they've dropped to the 60s, winds were still a problem.

"It's definitely gusty, but we're lucky, the winds are blowing away from homes," Kern County Fire Department spokesman Corey Wilford said. "It would be better if we didn't have winds at all though."

Lower temperatures are expected to persist into the weekend.

The fire has spread to three counties, Los Angeles, Kern and Ventura, but burned in mostly populated areas and threatened no homes or buildings.

A Kern County high school was closed as a precaution.

The fire started early Wednesday afternoon for reasons that remain under investigation. It initially burned thick brush, seasonal grasses and sage, but then moved into the trees.

The cooler weather helped firefighters overnight clear brush and create breaks in hopes of slowing the blaze. Efforts on Thursday were focused on the southern edge of the fire.

The cause of the fire is under investigation.