SACRAMENTO, Calif. -- Smoke from a large wildfire northwest of Fairfield and other blazes around Northern California continued to choke the skies around Sacramento on Monday, leading authorities to remind those with asthma and other respiratory problems to avoid the outdoors if possible.

The smoke was the result of scores of separate wildfires -- more than 800 as of Monday -- that flared over the weekend across the heart of wine country and remote forests. Many of the blazes were sparked by lightning.

Gov. Arnold Schwarzenegger proclaimed a state of emergency Monday in Monterey and Trinity counties as a result of numerous wildfires, officials said in a news release.

The proclamation utilizes all resources consistent with the state's authority under the California Disaster Assistance Act.

"I've been governor for four years and I've never heard that number (of fires) before, so it was quite surprising," Schwarzenegger said.

A wildfire that burned along the border of Napa and Solano counties near Fairfield burned about 4,000 acres of rugged terrain, but cooler temperatures aided firefighters in getting the blaze 60 percent contained as of Monday afternoon. The fire started Saturday.

One home and one barn were lost, but the flames largely appeared to be laying down. Evacuation orders remain in place for residents of Twin Sisters Road and Joyce Lane. About 250 homes are threatened, down from the 400 homes that were threatened on Sunday evening.

Meanwhile, firefighters said they have made good progress against the flames.

"It's much better today," said Chuck Joiner, a spokesman for Cal Fire.

However, firefighting crews are spread thin because of the amount of fires sparked by the lightning strikes.

"This is an unprecedented lightning storm in California, that it lasted as long as it did, 5,000 to 6,000 lightning strikes,"said Del Walters, assistant regional chief of the California Department of Forestry and Fire Protection. . "We are finding fires all the time."

Air quality in Sacramento and Roseville was unhealthy for all residents as of Monday evening, while air conditions were slightly better in Woodland, Davis, Folsom and Elk Grove, KCRA 3 WeatherPlus chief meteorologist Mark Finan said.

The smoky conditions and poor air quality will continue into Tuesday because the Delta breeze is not strong enough to clear out the region, Finan said.

"Smoke can affect anyone, but it's especially harmful to people who have existing breathing problems, like seniors or anyone suffering from asthma or emphysema," said Dr. Glennah Trochet, Sacramento County's health officer, in a prepared statement. "The fine particles in smoke can obstruct the airways, making it harder to breathe and reducing oxygen intake."

Grass Fires Burn Near Historic Town

Fire crews fought a series of grass fires near the Yuba River on Monday, with one of the blazes creating concern for the historic town of Washington.

A fire burning near the South Fork of the river had scorched at least 200 acres and was growing as of 4:30 p.m. Fire officials said if the fire crosses Scotchman Creek the town of Washington could be in danger.

Fire investigators said farm workers may have sparked a separate grass fire near Elverta Road and East Levee Road on Monday.

Workers were tilling a recently harvested field when tractors hit a rock sending sparks flying, officials said.

1,397 Acres Burn In Butte County

A total of 25 fires are burning in Butte County, charring more than 1,397 acres, fire officials said Monday.

The Butte County Sheriff's department has issued a precautionary evacuation for the Lake Concow Area because of a lightning fire that has burned 100 acres off of Rim Road.

The American Red Cross is setting up an evacuation center at the Spring Valley School.

Residents In Nevada County Return Home

Residents of Nevada County were back in their homes Monday after a blaze forced voluntary evacuations Sunday night near Bowman Lake.

About 25 fires were sparked over the weekend in the Tahoe National Forest. Crews are now focused on two blazes -- the Fall fire and the Clear fire. Those blazes have burned 450 acres. No homes have been burned.

Two dozen fires were also burning in Butte County. More than 300 acres were charred.

The Butte County Sheriff's Department issued a precautionary evacuation advisory for the Lake Concow area for a blaze burning just off Rim Road.

The Red Cross set up an evacuation center at Spring Valley Elementary School on Pentz Road in Oroville.

In Stanislaus National Forest, a blaze burned up to 500 acres about 19 miles northeast of Groveland and may spread into nearby Yosemite National Park. The flames are far from any populated areas.

Officials prohibited campfires, barbecues and smoking outside developed campgrounds in areas of the forest where fire danger is highest.

In San Mateo County, 200 residents in Brisbane were forced to leave their homes as a fire approached. The blaze started at about 7:30 p.m. Sunday. About 200 firefighters were battling the flames.

In the foothills of Mariposa County, firefighters were battling 3 wildfires on Monday.

The largest of the fires is called the Oliver Fire, which has burned 200 acres and has no containment, officials said.

The fire is threatening homes and residents are on stand-by for evacuations.

Wildfires have destroyed more than 175 homes in Northern California so far this year. Blazes started popping up in the region just as California's unofficial fire season began in mid-May, following the state's driest two-month period on record.

"My hat is off to all the firefighters out there on the ground, dirty, hot, smoky," Walters said. "And it's going to be a long road for us."

Governor Proposes Insurance Surcharge

Homeowners may see a new fee to cover firefighting costs under a proposal.

Schwarzenegger said he wants a annual surcharge on homeowners insurance statewide. The cost would be about $6 to $12 each year.

"Our idea is to raise the homeowners insurance, and I think everyone would benefit," Schwarzenegger said.