Red Cross volunteer Virginia Hart left her home in Richmond to go volunteer as flood waters filled the streets and evacuees filled the shelters.
Hart says the shelter was the only refuge around.
"Last night there wasn't a single restaurant open in the town that I'm in, but the shelter was actually serving dinner, so the services we provide are necessary and the people are extremely grateful and often become friends at some point," she said.
Nearly 11,000 people spent the night in Red Cross shelters after the storm drove them out of their homes.
This is going to take a vast amount of resources for us to respond to and we can certainly use all the help we can get," Hart said.
But there are other volunteers helping the Red Cross without ever leaving the Bay Area, answering a critical call for blood donations that stems directly from the storm.
Blood drives that were cancelled because of the storm are a big problem for patients who need platelets. The cells that give blood the ability to clot only last five days once they've been donated, so any extra donated in the Bay Area will make their way to hospitals back east.
"Not having two days of platelets is a real serious matter so we will be shipping platelets to the East Coast," Northern California Red Cross CEO Jeff Meyer said.