The National Weather Service says the dense gray smoke cloaking the Bay Area is coming from a raging, 15,000-acre wildfire in the Plumas National Forest near Greenville, about 150 miles northeast of Sacramento.
However, some of the smoke Contra Costa residents are seeing is coming from a 15-acre fire that is threatening several structures in a rural area east of San Ramon.
National Weather Service meteorologist Steve Anderson said winds expected to pick up late this afternoon should help clear the air throughout the Bay Area. "But right now the winds are blowing the smoke directly into the Bay Area," Anderson said.
He added that offshore winds died down overnight and fog dissipated, so smoke blowing in collected in the area. This afternoon as the Great Basin - eastern California and Nevada - heats up, the rising warm air sucks in cool air from the Pacific and should take a lot of the smoke with it, the Weather Service said.
The smoky air has done nothing good for air quality, but Karen Schkolnick of the Bay Area Air Quality Management District said Bay Area air quality remains within the healthy range.
The air board's monitors, including one in Livermore and one in San Jose, show only a slight elevation in particulate matter - the most troublesome part of air quality for humans, Schkolnick said.
However, she said, anyone who is susceptible to poor air quality should take precautions, keep windows and doors close, turn off ventilators. "You want to keep the smoky ar on the outside and minimize exposure," she said.
In Sacramento, Daniel Berlant, of the California Department of Forestry, said the Plumas forest wildfire is only 5 percent contained. More than 1,000 CDF and U.S. Forest firefighters are involved in the battle against the fire, he said. The cause of the first, which began Sept. 3, is still under investigation, Berlant said.
"It's really smoky here in Sacramento," he said. "We can't see blue sky at all."
The other big fire, the Lick Fire, named for the Lick Observatory on Mt. Hamilton, about 10 miles from the fire, is covering 11,000 acres and is about 20 percent contained, Berlant said.
He said the fire, which is in Henry Coe State Park between Morgan Hill and Gilroy is still actively burning and is being attacked with a CDF air tanker.
Fire crews from around the Bay Area have been called to fight the Lick fire.
The fire near San Ramon was first reported at 10:40 a.m. along Johnston Road, which is off Camino Tassajara, according to the San Ramon Valley Fire Protection District. No one was reported injured and no structures were lost at 11:45 a.m.
San Ramon Valley fire and Cal Fire have responded with 12 engines, two hand crews, three bulldozers and two air tankers.
Smoke from the blaze was drifting north to Walnut Creek, and as far
south as Pleasanton.