The blaze had charred nearly 42 square miles as of Friday in the Los Padres National Forest and destroyed 16 homes in the Big Sur area, one week after it was started by a lightning storm that also ignited more than 1,000 wildfires from the Central Coast to the Oregon state line.
On Saturday, President George W. Bush issued an emergency declaration for California and ordered federal agencies to assist in firefighting efforts in several counties including Monterey, which includes Big Sur. Gov. Arnold Schwarzenegger asked for the declaration on Friday, saying fires had charred more than 400 square miles.
Firefighters braced for the possibility of more lightning in Northern California during the weekend.
The Big Sur fire was only 3 percent contained. Firefighters concentrated on protecting more than 500 homes and other buildings threatened by the blaze and let the wildfire rage virtually unchecked in remote mountain wildernesses.
A roughly 12-mile stretch of coastal Highway 1 was closed in the area, shutting off access to several popular tourist spots. Thick smoke obscured iconic coastal vistas.
South of Big Sur, another fire in the Los Padres National Forest that started three weeks ago had burned 92 square miles (238 sq. kilometers) and destroyed 16 structures including two homes. It was 71 percent contained Saturday.
Areas hardest hit by the lightning fires include Butte County, where 31 fires had charred 19 square miles and threatened 1,200 homes; Mendocino County, with 121 fires that have covered 45 square miles and threatened 900 homes; and Shasta-Trinity counties, where 230 homes were threatened and 58 square miles of forest was charred by about 160 fires.
Some 11,000 firefighters from 41 states were battling the blazes.
The fire threat has already led communities to cancel plans for Fourth of July fireworks displays.
The blazes also have spread a smoky haze over much of the San Francisco Bay area and Central Valley, prompting air regulators to urge people to stay indoors. Air pollution readings in Northern California and the Central Valley were two to 10 times the federal standard for clean air, said Dimitri Stanich, spokesman for the California Air Resources Board.
Elsewhere, a blaze that had blackened nearly 2 square miles had forced 100 people from their homes near Guffey, Colorado, about 130 miles southwest of Denver. It was 10 percent contained Friday evening, said Steve Segin of the Rocky Mountain Area Coordination Center, which coordinates firefighting agencies.
It was one of a dozen fires started by lightning in Colorado on Thursday, but most of the others were controlled before spreading very far, Segin said.