From the San Francisco Chronicle:
Air quality officials have called a Spare the Air alert for Thanksgiving, meaning the burning of wood and manufactured fire logs is banned both indoors and outdoors from midnight tonight until midnight Thursday.
The use of any wood-burning device, including fireplaces, wood stoves, pellet stoves and outdoor fire pits, is illegal during that period, the Bay Area Air Quality Management District said.
The wood-burning ban covers Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, southern Sonoma and southwestern Solano counties.
Obviously, not something to be thankful for if you live up in the Bay Area of Northern California.