Steady rain and windy conditions flooded several roadways early Friday and created slippery driving conditions as the commute hour got under way.
The CHP said there was flooding on northbound Highway 101 at Golf Course Drive, with reports of up to 6 inches covering the fast lane, authorities said.
Two vehicles driving just south of there near Railroad Avenue crashed because of wet conditions shortly before 6:30 a.m., sending one vehicle up to 150 feet off the roadway, the CHP said.
Standing water also was reported on Highway 116 at Mirabel Road, while a vehicle slammed into a utility pole at Sebastopol and Stony Point roads in Santa Rosa.
A vehicle ran off Napa Road and into a ditch near Burndale Road in Sonoma, the CHP said.
In Mendocino County, recent rains apparently contributed to a huge sink hole across Highway 162 about a mile and a half east of Highway 101, Cal Fire said.
"It sounds like it's, like, 20 feet deep," with a tractor-trailer rig partly in it, Cal Fire Communications Officer Anthony Massucco said.
"It's impassable," he said.
Despite numerous crashes, there were no reports of major injuries.
Numerous trees had fallen around the North Coast overnight, though there were no immediate reports of structural damage or injury, Cal Fire and emergency dispatchers said.
The National Weather Service said gauges in the Santa Rosa area recorded between a half and an inch of rain in the previous 24 hours.
Coastal hills received more - up to 2 inches and more in the previous six hours, meteorologist Mark Strudley said.