Final answer:
Mountains maintain permanent snow cover at high altitudes due to lower temperatures, and it takes significant energy transfer for snow to melt even if air temperatures rise above freezing. Different climate zones exist along a mountain's elevation gradient, which can result in polar climate conditions at the summit despite warmer base temperatures.
Step-by-step explanation:
Mountains often have permanent snow cover at high elevations due to a combination of lower temperatures and atmospheric conditions. Snow remains on mountain slopes even when daytime temperatures are higher than the freezing temperature for several reasons. One is that snow is a solid form of water and requires substantial heat to undergo a phase change into water. Even when air temperatures rise above 0°C, it takes time for enough energy to be transferred to the snow to melt it.
Furthermore, temperatures decrease with altitude, so even if the base of a mountain experiences warm climate, the summit may still be cold enough to sustain permanent snow and ice. The term climate zones is relevant here, as high mountains can have different climate zones from base to summit. This phenomenon is often observed in high mountain ranges like the Rwenzori Mountains, which can have a tropical climate at their base but a polar climate at their summit.