If there is no power for a UV light, you can always use the old UV power source. Let him outside for a few hours a day. Setting a cage outside would help.
I'm not all that worried about my snakes either, as long as it doesn't get too hot. If it really did get hot inside, I could bag them and dampen the cloth bags to keep them cooler.
I keep a lot of water on hand for all the animals in new garbage cans with lids. Be sure to check them BEFORE you need them. I filled two BRAND new bins, and then discovered the next day that one had a small leak. LOL. I had "only" 50 gallons of water. Yes.. I agree that I'm a bit OCD about keeping enough stock on hand.