Wildfire Near California-Oregon Border 'Extreme,' Firefighters Say

SACRAMENTO, Calif., Sept 3 (Reuters) - Firefighters battling a fast-moving Northern California blaze said Wednesday they expect a second day of extreme conditions, as heat and high winds spur a lightning-sparked wildfire near the Oregon border.

The so-called Happy Camp Fire has been burning in the Klamath National Forest since Aug. 11, consuming 72,000 acres and costing an estimated $41 million so far in firefighting costs.

"Yesterday, we had an increase in extreme fire behavior ... and we do expect the same extreme fire today, said Paul Gibbs, a fire spokesman for the U.S. Forest Service.

Tuesday night, the Siskiyou County Sheriff's Office expanded an evacuation order for communities threatened by the blaze, and closed a portion of State Highway 96.

Previous evacuation orders had included about 250 homes, but neither Gibbs nor a spokeswoman for the sheriff's department had an estimate for the number of homes in the evacuation area as of mid-morning Wednesday.

The fire had slowed under cooler weather due to a temperature inversion over the Labor Day holiday, but flipped into extreme conditions on Tuesday as clouds cleared and winds picked up, Gibbs said, leading the fire to produce new burn spots a full two miles ahead of the main blaze.

"It's like opening up a damper on a fireplace," he said. So far, no buildings have been damaged by the fire. Eight firefighters have been injured battling the blaze.

More than 2700 personnel from 77 fire crews have helped to battle the blaze, originally a complex of 17 fires, Gibbs said.

The fire was 15 percent contained on Wednesday morning, and full containment was not expected until Sept. 20, he said. (Reporting by Sharon Bernstein; Editing by Bernard Orr)