Swift water rescue, and urban search and rescue teams are critical parts of dealing with major flooding.
In Marin County, they have 36 people assigned to do just that. It looks like they will be busy.
This time around, flooding may be more widespread and deep since the ground is already thoroughly saturated and tonight's high tide will make things worse says rescue team member Kentfield Fire Department Battalion Chief Dave Glenn.
SEE ALSO: Live updates about the Bay Area storm
"The tides today are supposed to be 6 foot 2. But with the storm surge. they're saying it could be a foot to a foot-and-a-half higher. The water that runs in the creeks has nowhere to go because it runs into the Bay. So when the Bay is higher the water has nowhere to go and it comes out of its banks and causes flooding," said Glenn.
That's why rescue teams are staged throughout the county.
"We have about seven of these [teams] throughout the county. We also have six rescue inflatable boats throughout the county and they're staffed with rescue personnel who are trained to rescue with them," said Glenn.
Water rescue happens not just in streams but flooded streets, inundated neighborhoods and creeks overrunning their banks.
"Ten or 15 years ago, we had swift water running through the streets… and it was like a river. It was doing so fast down there. The problem with that is there's all kinds of debris flowing down the river of the stream, whatever. The trees, trash cans, the basketball hoops, different stuff like that. So, that stuff is dangerous for the rescuers and the people because we get caught in it. So, we have to look out for that," said Glenn.
Trees falling into houses is a major concern.
"The wind is supposed to be really high later this afternoon until later tonight. They're saying 20 to 30 miles an hour with gusts up to 50. So, the trees are saturated and the roots are saturated and the trees might fall down to and that could cause a lot of different problems," said Glenn.
Despite all their training when they are in swift water or collapsing buildings. they're in as much danger as the people they're trying to rescue. Yet, they go on and do it.