It's rained all night and will continue through much of the day with heavy rain at times across the Bay Area off and on through next Wednesday.
National Weather Service forecaster Steve Anderson said the surf and winds will not be as high as during a storm that hit the region this past Sunday.
"It's mostly going to be a rain event," Anderson said.
Weather service officials expect two to four inches of rain in the North Bay, one to two inches in San Francisco and about an inch in both the East and South Bays, according to Anderson.
The above normal rainfall will be near the Oregon border, where 10 to 12 inches is expected, he said.
He said the storm is not going to be an El Nino event but rather another winter storm.
National Oceanic and Atmospheric Administration officials are predicting extreme high tides, called King tides, in Marin County from Monday through Wednesday before Christmas.
High tides, but not King tides, are forecast for Christmas Eve, Christmas Day and the day after Christmas, NOAA officials said.
Marin County sheriff's officials said the high tides and King tides will likely flood roads, and the flooding could mean those traveling have to take a different route.
Caltrans told sheriff's officials that the potential for flooding will last until Dec. 28.
Sheriff's officials are reminding drivers to avoid driving through ponded water and to allow extra time for travel during peak commuter times and on holiday travel days.