Temperatures dropped below freezing around the North Coast on Saturday, causing icy conditions on roads around the region, and were expected to do so again Sunday, creating the potential for more black ice.
"It will still be really cold," meteorologist Austin Cross said. "And so people should protect their pets and take any sensitive plants inside, and definitely watch for any ice on the roads."
Santa Rosa's low temperature early Saturday was 24 degrees, a record, with only a few places in the North Coast escaping the 20s.
The low in Calistoga, Cazadero and Middletown also was 24 degrees, with 30-degree low temperatures in Boonville, Bodega Bay and Sea Ranch.
The cold was to continue through Sunday, with a deep freeze warning in effect for Lake County, meaning temperatures could drop below freezing for five hours or more, the weather service said.
"One more chilly night and then a warming trend begins," forecaster Steve Goldstein said.
Sonoma County road crews maintained a busy pace on Saturday, sanding rural roads around the county, from Alexander Valley to Crane Canyon Road, Graton and Sebastopol to Porter Creek Road.
Icy patches that formed in residual rainwater in a Highway 101 construction zone through Rohnert Park caused two or three cars to spin out shortly after 5 a.m. after they "went through it too fast," CHP Sgt. David Derczo said.
There were no major injuries, the CHP said.
In general, authorities around Lake, Mendocino and Sonoma counties reported no significant problems, however.