What are clouds and why does it rain?

Most of us, especially if you live in the UK, see clouds every day. Sometimes they are fuffy white things floating along on their own, and other times they combine to form a dark layer that covers the sky and threatens rain at any moment. Have you ever wondered what happens to make a cloud form, or why some clouds produce rain whilst others seem to do nothing at all?

Well, the air around us contains water, but you can't see it because it exists as a gas. We call it water vapour. Warm air can hold more water than cool air, so when warm air that contains plenty of water vapour is cooled down it has to lose some of its water. This condenses out ( or precipitates) as fog or cloud. Whether or not you end up with a little white fluffy cloud or a massive grey rain machine depends on several things, including how much water is precipitated and what caused the air to cool.

There are three main ways in which this happens in the atmosphere, and every geography student needs to know, and understand, all three of them. To learn more, visit What are clouds and why does it rain?

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