Spraying hot water all over everything is just going to work temporarily. The water is going to cool and since the heat is out it is not going to evaporate like usual and instead just get cold and leave the cage wet.
Apart from a small propane heater you can fill water bottles with hot water and then place them in a couple layers of tube socks. This will give your snake a nice warm object to wrap around and you can easily heat them over. This works if you have gas appliances.If you don't you can keep hand and foot warmers(the disposable kind) on hand. Be very careful with these as they get VERY HOT. They will need to be wrapped in socks and tested before throwing them in to your snakes after you let them sit a few minutes to see what temp they reach. Not that the water bottle doesn't need to be checked, but these produce the heat instead of loose heat like the water bottles.