Why does snow stay on mountain tops?
Three factors, acting alone or in combination, allow snow to remain on mountain tops well into summer and even all year long: temperature, snow quantity, and sunlight (or lack thereof). Many higher mountains are so high that the temperature at their tops rarely climbs far above freezing, even in the middle of summer. Massive amounts of snow can create snow drifts so deep that it may take until July or even August for it to melt. This, combined with the lower temperatures at high altitudes, enables snow to remain on mountain tops long after it’s melted from the lower areas. Finally, since the sun in Alaska remains relatively near the horizon in the summer, the northern sides of many mountain tops receive little direct sunlight, slowing the melting of the snow.
