I would forget the food. Make sure they are given water access as much as possible though. Most snakes can last a month or two without food. Water is a necessity however.
We are about 35 miles Northeast of New Orleans (about 20 miles from where the eye of Katrina hit). It sucks that we will probably be on the strong side this time......but we plan on staying unless conditions get really severe (i.e. Catagory 5 hitting New Orleans directly, putting us in the very worse of it).
For Katrina, we did not have power for almost a month. But we now have a few generators, so I am making preperations to get the reptile collection 'consolidated' and easily moved to an air conditioned room.
I would also do a search on this site for more information. We had several discussions after the Katrina season.
The heatpacks and handwarmers will be too much for most conditions. The temperatures this week in the southeast are 90+ deg. I would be more concerned with the animals getting too hot than being cold. Heat kills animals quick.