For temporary short term heat, I'd recommend the hot water bottle method as well. You can heat the water up higher than 94 and drop the water bottle in a sock or something to insulate it and keep the snake from coming in direct contact with the bottle. Drop it in the snake tub and it will at least give them something warm to wrap around if they get too cold... Not a very helpful suggestion if nobody is physically with the snakes to do this though. Sorry for the situation you're in. Definitely take steps to prepare for such emergencies as soon as you can...