1. In general, the outer boundary of a snow-covered area. It has at least two specific applications: 1) the actual lower limit of the snow cap on high terrain at any given time; 2) the ever-changing equatorward limit of snow cover, particularly in the Northern Hemisphere winter. 2. Same as firn line. See climatic snow line.

the line on a mountain above which there is perpetual snow and ice

The boundary above which snow remains all year.

The elevation above which snow can form and remain all year.

the minimum elevation of snow lying on the ground or glacier surface; the snow line at the end of an ablation season marks a glacier's current equilibrium line.

The lowest elevation area of a perennial snow field on high terrain, such as a mountain range.

The snow line is the point above which, or poleward of which, snow and ice cover the ground throughout the year.