When we lived in northern Michigan unfortunately power outtages were far too common with the winter weather up there. What we did was keep a very good supply of instant warmer packs (you can get ones that last for hours upon hours). We also had a pile of heavy work socks. When any big storm hit, we would immediately pop up the heat in each enclosure a bit and if the power went out we immediately covered every enclosure in blankets and popped one or two of the heat packs into a sock. Knot in the sock, tuck it in right beside a hide and there you go...a nice warm spot for the snake. With the big boa we had for a time there was some concern she could actually try to ingest the sock so for her I would put the sock into a large margarine container (much bigger than she could eat). I cut many diamonds out of that container so it became basically a safe heat radiating thing. Got us through a few storms with no snake the worse for the wear.