More than 134,000 acres have burned in a series of California wildfires that were mostly sparked by lightning last week, fire officials reported this week.
The wildfires have been difficult to fight because most are burning in remote and unforgiving terrain, according to Amy Head, a spokeswoman with the California Department of Forestry and Fire Protection.
More than 7,500 local, state and federal fire crews had been battling the massive wildfires ravaging Northern and Central California, she said.
Three fires sparked by lightning have continued to rage in the Shasta-Trinity National Forest. Lightning activity ignited more fires this week, prompting an air attack from firefighters parachuting in, according to the U.S. Forest Service.
Fires in Siskiyou County, also started by lightning, have ravaged roughly 34,000 acres, prompting voluntary evacuation advisories Friday for residents who live in Idlewild, Taylor Lake and Robinson Flat.
Meanwhile, two wildfires -- each more than 30,000 acres -- in the Lassen National Forest are winding down, fire officials said.
The massive series of fires burning along the California-Oregon border has resulted in a great amount of smoke.
Although the North Coast Unified Air Quality Management District hasn't issued any advisories, officials said the smoke contains harmful chemicals that can affect those with respiratory and heart disease, young children and older adults.
In some instances, "fire clouds" have formed over the region, creating dramatic aerial scenes that were captured by a fighter jet.