Nathan,
Last year for Hurricane Katrina, we lost power for 31 days. I tried to run my Helix's with my generator, but they would not work, and kept giving me error messages. My guess is that the power supplied by the generator was not tolerated by the thermostats. However, I kept a close eye on my snake room, and kept a box fan running. The temps in my snake room hung out around 90 degrees for the majority of the month that we had no power. I noticed very little impact to my snakes. Most of them ate fine. However, my rats were not happy with the excessive temperatures. The best I could do was to try to cool the rat room as cold as I could get it before I went sleep every night. My logic was that the rats were most active at night, so I wanted them to be as comfortable as possible during the peak of their activity. I would run the A/C for about 1.5 hours, and drop the room down to about 65 degrees. By the time I woke up, the temps would be in the upper 70's. During the day, the rats would sleep most of the time anyway, and we ran a fan to keep them as cool as possible. Rat production did drop during our power outage, but it did not hurt us to bad. I don't know if this really helped you prepare any for what could help in the same situation, but I just wanted to relay our story of what we did.
Sincerely,