Wildfires burning through dry terrain in West Coast states have forced scores of evacuations as fire teams worked to corral the blazes.

Lightning sparked dozens of fires in Northern California, including one in rural Modoc County that spurred some 120 people to evacuate, and the threat of more strikes along with winds from looming thunderstorms could aggravate the firefight.

Authorities in Siskiyou County near the Oregon border issued an evacuation notice late Friday.

The most dangerous of the fires was near the community of Day and had burned through nearly 18 square miles of brush and heavy timber and was threatening 150 structures Friday, two days after it began. It was only 10 percent contained.

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.

Nearby, on the California side of the border, the Siskiyou County Sheriff’s office issued an evacuation notice late Friday night for residents of Beaver Creek. Fire officials said deputies were personally informing residents. There was no word on the number of homes affected by the notice.

California is in its third year of drought, which has heightened the fire danger. The California Governor’s Office of Emergency Services announced Friday that it has asked the state’s National Guard to activate specially trained helicopter units to help fire agencies.

“The forward deployment of these will help incident commanders and the personnel they are directing save lives, homes and personal property as well as valuable watershed by providing critical resources within a moment’s notice,” California emergency services Director Mark Ghilarducci said in a statement.

Fire crews in California also were battling a blaze in Sierra National Forest about 60 miles northeast of Fresno that threatened dozens of homes and forced a handful of evacuations Friday afternoon.

Evacuations were ordered for some 50 houses in Arnold Meadows, but many are vacation homes and only about a dozen people had to evacuate when deputies went door-to-door, The Madera County Sheriff’s Department said.

The blaze was burning close to the Mammoth Pool Reservoir, a popular recreation spot that supplies drinking water, said fire spokesman Matthew Chambers.

The blaze had burned through nearly 13 square miles and was 15 percent contained.

In Yosemite National Park, residents from about 50 homes returned Friday afternoon. They were the last remaining evacuees from a fire that had burned through 7 square miles and destroyed a home and a duplex. It was 78 percent contained.

The park remained open and was largely unaffected.