The fires burned about 70 acres and were contained at 4:47 p.m., Cal Fire spokeswoman Jennifer Neal said.
A dozen fire departments responded to as many as 10 separate brush fires near Stony Point Road and state Highway 116, and along U.S. Highway 101 south of Cotati and Rohnert Park and north of Petaluma.
Neal said she could not confirm reports some structures were threatened.
The largest fire was two or three acres, but some of the fires were merging, Cal Fire spokesman Dustin Nishimura said.
The fires were reported at about 3 p.m. They were burning on Stony Point and Jewett roads, Pepper and Meacham roads, Roblar Road and Debbie Hill Road.