The lower altitudinal boundary of a snow-covered area, especially of one that is perennially covered, such as the snowcap of a mountain.
The fluctuating latitudinal boundaries around the polar regions marking the extent of snow cover.
The boundary marking the lowest altitude at which a given area, such as the top of a mountain, is always covered with snow.
The boundary marking the furthest extent around the polar regions at which there is snow cover. The polar snow lines vary with the seasons.
