Evacuations orders have been issued in Santa Cruz County due to flooding Wednesday morning.
The National Weather Service has also issued a Flash Flood Warning for parts of Marin, Sonoma, and Napa counties because of heavy rain that is already causing flooding in some locations.
There is a Flash Flood Warning in effect for Alameda County until 3:30 p.m.
The warning was issued for southeastern Marin County until 11:15 a.m., southeastern Sonoma County until 2:15 p.m. and southwestern Napa County until 1:15 p.m., according to the weather service.
Flash flooding is already occurring in Fairfax Creek in Marin County and is imminent in other locations in the county such as Corte Madera and Mill Valley, weather service officials said.
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Gauges in the Laguna de Santa Rosa and Petaluma areas in Sonoma County also show high water levels, as well as many locations in Napa County such as Napa, St. Helena, Calistoga and Yountville, according to the weather service.
FULL LIST: Storm triggers closure of dozens of schools in Marin and Sonoma Counties.
Relentless rain has also turned a popular highway in the North Bay into a river. Highway 121 near Highway 12 flooded in Schellville overnight. Three cars got stuck in the flooding and six people were rescued by firefighters. All of the rescued are expected to be okay.
Some residents in Kentfield make light of the flood waters and took out the kayaks to check out the damage.
"Koi Pond is under water, so I hope the fish are okay. The house is okay. The Red Cross came in a long time ago and raised all these houses to get them up out of the flood water," said Laura Roxon, a Kentfield resident.
REAL-TIME: Track the rain on Live Doppler 7
Tuesday's storm is a 3 on our Storm Impact Scale. Meteorologist Mike Nicco says the storm is expected to bring moderate to heavy rain throughout the day, and will taper off late this afternoon.
MORE INFO: ABC7 News Storm Impact Scale explained
The higher rainfall total and potential for flooding meet level 3 storm criteria.
RELATED: RELATED: Mike Nicco's Tuesday Morning weather forecast
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Bay City News has contributed to this report