How heavy are clouds?

Of course, you cannot answer this question in general, because every cloud has a different size and thus may have a different weight and there is also a difference between "light" good weather clouds and heavy storm clouds.

However, I can give you a rough order of magnitude, which is everything but not light. Although clouds are mostly made of very, very small water droplets which are often only a few micrometers in size, we have to take into account that even small clouds are consisting of an incredible amount of these droplets. So, even when looking at fair weather clouds only having a size of 200 x 200 x 200 meters, we can quickly reach a weight of 5 to 10 tons. Since 1 liter of water is equivalent to 1 kg, even such a small cloud 10 contain 5,000 to 10,000 liters of water.

Of course, powerful storm clouds or rain clouds are much more heavier! Such clouds can even contain ice crystals and much more larger water drops at higher altitudes and low temperatures. There is hardly a limit to the weight. Even a weight that goes into the millions or billions of tons, is not uncommon. 
2013-09-12 at 12:35