Not all bird baths can be left outside during the winter. In general, concrete, ceramic, and heated bird baths can withstand freezing temperatures, but check your brand’s guidelines just to be safe.  If you need to winterize a bird bath, start by cleaning it thoroughly with a weak bleach solution to prevent algae growth, and move it to a location that will get direct sunlight throughout the winter months. Line the bottom of the basin with a thick plastic sheet, weighing it down with rocks as needed, then use twine or zip ties to secure the covering around the pedestal and base of the bird bath. This will help protect it from the harsh weather. You can also place an immersible heater into your bird bath to prevent ice from forming.