Why do mountains have snow on top?

Answer: Temperature drops with altitude

Clouds drop snow there — Wrong. While precipitation does fall from clouds at high altitudes, this doesn't explain why it's snow rather than rain, or why snow stays on top. The key is that temperature decreases with altitude.

Temperature drops with altitude ✓ — Correct! Temperature decreases about 6.5°C per 1000 meters of altitude. This is called the environmental lapse rate. Above a certain altitude (the snow line), it's cold enough for precipitation to fall as snow and for snow to remain frozen year-round. Even tropical mountains can have permanent snow at high elevations! The thinner air also holds less heat.

Mountains are closer to clouds — Wrong. Being closer to clouds doesn't make it colder. In fact, clouds form at various altitudes. Mountains have snow because temperature decreases with altitude due to lower air pressure and thinner atmosphere, which holds less heat. It's the cold temperature that creates and preserves snow.