While I haven't lost data from the hurricanes or tornadoes, I know some that have. Their backups were in the same building as the main pc-obviously not a good idea. They also had a lot of the data stored at home, but in the same county...and lost that too.
Having some of it backed up to dvd's helped a lot-that let them recover much of it, as a lot of the damage was from water, which didn't immediately affect the dvd's. Note though, I said immediately. I made him send me the dvd's while he was sorting out power et al, and I copied the dvd's, then burned everything to an external drive for him.
A few months later, when he took out the dvd's, they all had fungus growing in between the layers-yuck!