The Petaluma River reached flood stages Sunday morning, and forecasters warned heavy rainfall was expected to continue throughout the day.
The National Weather Service's flash flood warning was in effect until 12:45 p.m. for the Petaluma area.
"The river is coming up in a hurry," meteorologist Diane Henderson said.
Stream gages at Willow Brook at Penngrove Park, Willow Brook at the Old Redwood Highway Bridge and Willow Brook at Stony Point Road were at or above flood levels.
Rainfall caused problems throughout the county.
Emergency dispatchers at 10:07 a.m. sent crews to Jesse Street in Sebastopol, where a tree reportedly fell into a home.
At least an inch of water flooded a house north of Healdsburg on Terra Holland Lane off Alexander Valley Road.
Crews were assisting a motorist heading toward Freestone who drove into standing water at Freestone Valley Ford and Freestone Ranch roads and became stuck.
Mud slides closed Highway 128 west of Cloverdale and Annapolis Road east of Highway 1.
Several vehicles slid off roads throughout the North Coast, and one single-car crash closed the Highway 101 Airport Boulevard off-ramp as crews worked to remove a grey Acura that hit a utility pole.
Petaluma received 0.87 inches of rain during the 24 hours ending 8 a.m. Sunday. Cloverdale received 1.3 inches and 0.46 inches fell at the Charles M. Schulz Sonoma County Airport.
In Petaluma, high tide forecast for 10 a.m. was expected to worsen flooding, said Petaluma Fire Battalion Chief Jeff Schach.
Low-lying areas, especially businesses around Industrial Avenue, should expect some flooding.
For a complete list of road closures in Sonoma County, visit http://roadconditions.sonoma-county.org.
Search for Cal Trans road condition alerts at http://www.dot.ca.gov/cgi-bin/roads.cgi