In the Bonny Doon area, about 10 miles northwest of Santa Cruz, a wildfire quickly grew to one square mile after it broke around 3 p.m. Wednesday. It was unclear how many structures had been damaged, fire officials said.
Evacuations were ordered for 500 residents in the heavily forested hills. Voluntary evacuations were in place for another 1,000 residents.
Nearly 800 firefighters were battling the blaze, which could spread to as many as 1,500 acres, Battalion Chief Paul Van Gerwen said.
Hot temperatures and tinder-dry vegetation prevailed throughout Northern California, where hundreds of firefighters were deployed on fire lines from the North Coast wine country to the Central Valley.
Gov. Arnold Schwarzenegger declared a state of emergency in Butte County late Wednesday to free up additional firefighting resources. He declared another one in Santa Cruz County early Thursday.
Farther south, the state's largest wildfire had charred more than 16,000 acres in the Los Padres National Forest and was only 16 percent contained.
The fire had spread east to a remote part of the Army's Fort Hunter Liggett and was moving toward the incident command post Thursday. But winds were driving the flames away from inhabited areas of the military base, said Manny Madrigal, a spokesman for the U.S. Forest Service.
Fort Hunter Liggett spokeswoman Helen Elrod said four families with homes near the base were evacuated, but the 5,000 military personnel who live there were not in immediate danger.
Wildfires on Tuesday destroyed 32 homes in Stockton, about 50 miles south of Sacramento, and 21 homes in Palermo, about 60 miles north of the state capital.
Meanwhile, a southeastern Colorado wildfire that started on a military training site doubled in size in one day. On Thursday, about 125 firefighters were fighting the fire, which scorched more than 60 square miles of remote and rugged country.
Officials believe lightning sparked the blaze. No structures are threatened.
The fire has not been contained at all and low humidity, high heat and gusting winds have hampered efforts to control the fire, said Capt. Gregory Dorman of Fort Carson.
In Colorado's Crowley County, prosecutors have decided not to file criminal charges against a man accused of causing an April wildfire that killed two volunteer firefighters, destroyed 22 homes and burned 14 square miles of prairie grass.
District Attorney Rod Fouracre said Wednesday that the fire was an accident.
The Crowley County sheriff's office, however, planned to issue a summons to Sam Martson, who allegedly violated a county ordinance by not getting permission to start a prescribed burn on April 14, Fouracre said. Violations of the ordinance are punishable by a fine of up to $1,000.
In far eastern North Carolina, smoke from a more than 60-square-mile wildfire was having a serious effect on air quality hundreds of miles away. The state issued a Code Red notice forecasting unhealthy air Thursday and Friday for the Triangle area of Raleigh, Chapel Hill and Durham, as well as the Rocky Mount area.
Lightning ignited the blaze June 1 on privately owned land and it has burned in and around the Pocosin Lakes Wildlife Refuge ever since. Firefighting officials say there is little they can do to extinguish the wildfire until a massive rainstorm falls.