What i used to do if it got below 70F in the snake cages, was pack them all in their sterilite tubs and put them in the car and go to sleep in my car with the engine running and heater set on mid. Made for an uncomfortable night but at least the snakes were warm. Snakes are not going to be hurt by 70-75F temps for a few hours. Heck i believe in the mountains in Peru where BCL come from, it can get down to 50s or 60s at night and they live there fine. You might be surprised how cool of temps snakes can tolerate. It's the high temps that will kill them fast or scramble their little brains.