Well, I know that most datacenters keep back up generaters. For example, Nocster keeps a 500 gallon generator that can run the entire datacenter for like 72 hours or longer. Of course, if a hurricane came through, it might knock out the bandwidth provider lines going into the datacenter, so therefore, a backup is useless.
The datacenter itself is quite structurly secure for high winds and severe rain. Floods are another story, but I'm assuming they have a solid foundation that's high enough off the ground to protect the machines for average minor floods.