The climatic snow line is the point above which snow and ice cover the ground throughout the year. The actual snow line may seasonally be significantly lower.
The interplay of altitude and latitude affects the precise placement of the snow line at a particular location. At or near the equator, it is typically situated at approximately 4,500 meters (or about 15,000 feet) above sea level. As one moves towards the Tropic of Cancer and Tropic of Capricorn, the parameter at first increases: in the Himalayas the permanent snow line can be as high as 5,700 metres (18,700 feet), whilst on the Tropic of Capricorn no permanent snow exists at all in the Andes because of the extreme aridity. Beyond the Tropics the snow line becomes progressively lower as the latitude increases, to just below 3,000 metres in the Alps and falling all the way to sea level itself at the ice caps near the poles.
In addition, the relative location to the nearest coastline can influence the altitude of the snow line. Areas near a coast might have a lower snow line than areas of the same altitude and latitude situated in a landmass interior due to more winter snowfall and because the average summer temperature of the surrounding lowlands would be warmer away from the sea. (This applies even in the tropics, since areas far from the sea will have larger diurnal temperature ranges and potentially less moisture, as observed with Kilimanjaro and presently glacier-free Mount Meru). A higher altitude is therefore necessary to lower the temperature further against the surroundings and keep the snow from melting.
Furthermore, large-scale oceanic currents such as the North Atlantic Current can have significant affects over large areas (in this case warming northern Europe, extending even to some Arctic Ocean regions).
The highest mountain in the world below the snow line is Ojos del Salado.
Compare the usage of "snow line" indicating the boundary between snow and non-snow.