For future reference, I asked a vet about what to do when the power goes out. This is what he said.

If you have a good solid styrofoam container, ie, the one he may have been shipped in, put warm to hot water bags in the bottom with a thin towel or paper towel on top, then put the snake in. Another option is to put the snake in a sack and then put it on the water bags.

Option 2 is to use your own body heat. He suggested putting the snake in a sack and leaving it on your stomach under your shirt, or letting the snake coil around your neck. This effect is even better if you can take a hot shower beforehand.

Dont keep the snake in the box for more than 12 hours at a time, though I didnt go any more than 8.