Snow falls in Earth's regions that experience freezing temperatures and regular precipitation. Snow covers much of the Earth's polar regions for the entire year. At lower latitudes, snowfall varies according to season and elevation, and consistent coverage occurs only in places with high elevation and cold climate, according to NASA's Earth Observatory webpage.
Outside Earth's frozen polar regions, only a few geographic locations maintain snow cover all year long. These areas include the Himalayan mountains, which span the Tibetan plateau, the Andes mountains in South America and parts of the Rocky Mountains in the United States and Canada.
Numerous locations experience snow cover for at least part of each year, NASA reports. In general, there are more of these locations in the Northern Hemisphere than in the Southern Hemisphere. In both hemispheres, snowfall may occur in any area where the temperature drops below freezing, which is 32 degrees Fahrenheit, and water vapor or precipitation is able to freeze and form ice crystals. In such places, these crystals fall to the ground in the form of snow and ice, depending on their content and consistency. If the ground temperature is also below freezing, the snowfall accumulates and remains until warm temperatures persist for long enough to melt the snow and warm the Earth beneath.