Why does snow come out of clouds instead of rain when it is cold? — Grace of Pagosa Springs, CO

Dear Grace,

Colorado receives a good bit of snow every winter, doesn’t it? It does not snow often where I live (Montgomery, Alabama). The reason for this is also the answer to your question. As the Sun heats the water on lakes, oceans, and ponds, it changes from liquid to vapor, and floats up into the sky. This is called evaporation. When it cools down, it changes from vapor into tiny water droplets. This is called condensation. Clouds are made up of millions of water droplets that have condensed from water vapor. Air currents and wind keep the droplets of water in the sky. As the droplets bump into each other, they join together. This makes them larger and heavier. When they get heavy enough, they fall to the ground as rain.

Snow is different. In cold places, the water vapor freezes into crystals. When many of these little crystals gather together, they become heavy enough to fall as snow. If the air around Montgomery, Alabama, were as cold as it is in Colorado, it would snow more often here too!