The higher one goes, the colder it becomes. This affects water as well when it falls to the earth. If it falls in an area that is cold such as high elevation areas, it would end up freezing up and becoming snow.
When this happens, it would usually be stored in an area with other snow such as a snowfield or a glacier. This is why high mountains usually have snow caps. Mt. Kilimanjaro for instance in is Mid-Africa, a region which gets no snow whatsoever yet, it still has a snow cap.
