UPDATE 10 a.m. Saturday: This intersection re-opened at 9 p.m. Friday and remained clear this morning, according to Schell-Vista Fire Department.
North Bay residents are used to seeing Highway 121 flooding at the intersection with Highway 12, south of Sonoma, during heavy rains.
But vehicles don't always get stuck there and have to be towed.
"We try to close the road before that happens," a Highway Patrol officer told Patch on Friday.
But at 4 a.m. Friday, Sonoma Creek started backing up and it wasn't long before some cars were stranded.
CHP closed the highway at 5:30 a.m. due to "extreme flooding." Four vehicles had to be left on the road because it wasn't safe to send tow trucks in to remove them, spokesman Jake Ramos told Patch.
Ramos said it's possible Highway 121 may open at about 4 p.m.
Caltrans scraper trucks are attempting to move water off the highway, as tow trucks remove vehicles.
Motorists are taking Watmaugh Road out of Sonoma to Highway 12 and Napa Road.
We will continue to update storm coverage on Sonoma Valley Patch.