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Why does the elevation of the snow line vary with latitude?

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A car drives along the Trans-Canada Highway with Mount Sir Donald's sharp, snow-capped peak rising above forested slopes in the Selkirk Mountains, British Columbia. — mountain Mount Sir Donald in the Selkirk Mountains, British Columbia, looms above a segment of the Trans-Canada Highway.

The snow line—the lower limit of permanent snow cover—varies in elevation primarily due to differences in temperature and snowfall across latitudes.1

Because the snow line is defined by the point where annual snowfall accumulation equals ablation (melting and evaporation), its altitude is dictated by regional climate. In polar regions, where temperatures are consistently low, the snow line is found at a very low elevation. Conversely, in equatorial regions, where temperatures are significantly higher, the snow line is located at a much higher altitude.1

For example, while the snow line can reach sea level in subarctic regions, it rises to approximately 5,500 metres (about 18,000 feet) at 15–25° N and S latitude. Beyond these broad latitudinal trends, local factors such as slope aspect, wind exposure, and the amount of precipitation also influence the specific elevation of the snow line on any given mountain.21