How Do Clouds Float?

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Clouds float because the water droplets that comprise them are so incredibly tiny that they do not fall very fast. As clouds frequently occur in places that are experiencing updrafts, the force of the air pushing them up offsets the weight of the water droplets. In a cloud of typical size, the water droplets often weigh approximately 1/1000th as much as the air that containing them does.

The characteristics of the updraft that helps to form the cloud alter the effects produced by the cloud. For instance, strong summer thunderstorms are often associated with very strong updrafts. These strong updrafts help keep the condensed water aloft for extended periods of time. Eventually, the water droplets grow large and precipitate abruptly and quickly. By contrast, stratiform clouds, which produce light, steady rain, are associated with less powerful updrafts. The rain droplets quickly grow to a size at which they weigh enough to fall. This happens gradually and slowly in such clouds, thus causing light but consistent rain.

If the updrafts in a cloud are strong enough, they can carry the falling water droplets back up into the sky. When this happens, they may freeze once they reach a high enough altitude, which causes them to fall again. When this happens, hail is produced.