A cloud is made up of many, many tiny ‘clumps’ of water, either liquid or frozen.

The liquid droplets are about 0.002mm across – smaller than the thickness of a human hair. Some of these tiny droplets are so small that it would take a million of them to make a single raindrop!

Different clouds carry different amounts of water. After all, cloud shapes and sizes can range from thin wispy cirrus, right up to the monstrous cumulonimbus thunderclouds.

A typical cumulus cloud carries about 0.5g of water – the weight of a big garden pea – in each cubic metre. The cloud might be 1km wide, 1km long and 1km high, so it could contain up to 500 tonnes of water!

Air (when it is moving very fast) can easily hold up a jetplane that weighs 600 tonnes. So a lot of slowly moving air can easily hold up a 500-tonne cloud!