Twice in the last two winters we have lost power. 11 days for the first one and 9 for the second one. It got really cold in the house, but not like outside. I didn't have the luxury of seeking out a hotel or friends house, because everyone was in the same boat.
I suggest filling the tubs of the snakes with a lot of substrate. This will probably put them into a sort of "brumation" mode. My snakes dug right in and all made it through the whole thing just fine. Corns are very hardy and don't just inhabit warm climates, in the wild.
If you have to, safely use bees wax candles in their room and hand warmers.
Wayne