Officials were expected to send additional fire crews to supplement the 700 or so firefighters battling the blaze, which is burning in heavy brush and steep terrain amid the thunderstorm threat, said state fire spokesman Dennis Mathisen.
"It's a challenging firefight due to the extreme fire conditions we're experiencing," Mathisen said.
The fire was among more than 40 that have broken out as a result of lightning strikes since Wednesday. Most were in remote areas and were not threatening homes, and many of them were quickly contained.
In Washington state, a new wildfire burning intensely amid high winds forced the evacuation of about 200 homes Friday.
Officials ordered the evacuations and closed part of state Highway 20 because of the surging fire that started in north-central Washington halfway between Twisp and Winthrop.
Janet Pearce, a spokeswoman for Washington's Department of Natural Resources, said some structures had burned. It wasn't known if they were homes or other buildings.
The fire burned close to a command post at Liberty Bell High School, where firefighters working on the Carlton Complex have been camping in tents.
"We were a little nervous, but the fire's gone around us so now we're fine," Alan Hoffmeister, a spokesman for the Carlton Complex, told The Associated Press. "We sent over quite an air force of helicopters and air tankers to drop retardant. They really pounded it."
Washington state's Carlton Complex fire has burned 395 square miles and destroyed about 300 homes.
Along the Oregon-California border, a wildfire touched off by lightning has burned buildings and prompted evacuations, but there are no reports of any injuries.
Air crews over the fire reported the damage to multiple outbuildings, which could include barns, sheds and other uninhabited structures.
Fire officials say residents of 23 homes have been urged to evacuate. The said the blaze has destroyed three homes, five outbuildings and several cars.
Gov. John Kitzhaber invoked the state's Emergency Conflagration Act on Friday, requiring the state police and fire marshal to mobilize equipment, firefighters and other personnel from around the state.
The Oregon Gulch fire doubled since Thursday night to about 17 square miles, or just over 11,000 acres.