Winterize your fountain.
Drain the fountain. Unplug the pump and drain all the water from the fountain. Some fountains have a plug on the bottom for easy draining. Also, if your fountain has an auto float, turn it off as well.
When temperatures drop below freezing, the water in your fountain will freeze, cracking your fountain. Even if the water is running, droplets will jump out of the stream and hide in small cracks along the walls of your fountain. As the water freezes and melts, expands and contracts, the walls of the fountain will weaken and crack.
If you have a disappearing fountain, simply remove the PVC pipe from inside the urn, and let it drain. Once you are ready to turn on the fountain. put back the pipe and make sure it is not loose. Fill the urn with water and turn it back on.
Also, if you have an auto float installed in your fountain, please turn it off as well. You can cover your fountain with tarp to protect it even more from the cold weather.