Cumulus clouds are detached, individual, cauliflower-shaped clouds usually spotted in fair weather conditions. The tops of these clouds are mostly brilliant white tufts when lit by the Sun, although their base is usually relatively dark.

Since air has weight it must also have density, which is the weight for a chosen volume, such as a cubic inch or cubic meter. Clouds are made up of a lot of tiny water droplets, so they have weight and density. Clouds float because the density of the same volume of cloud material is less than the density of the same amount of dry air. Just as oil floats on water, clouds float on air because the moist air in clouds is less dense than dry air. But clouds are heavy.

Scientists have worked out that the water density of this cloud type is around 1/2 gram of water per cubic meter.

Research at the US National Centre for Atmospheric Research, calculated that the average cumulus is about a kilometer across and roughly has the shape of a cube, so it's as tall as it is wide.

One estimate of cumulus cloud density is given at a density of about 0.5 gram per cubic meter. A 1 cubic kilometer (km3) cloud contains 1 billion cubic meters.

Doing the math: 1,000,000,000 x 0.5 = 500,000,000 grams of water droplets in our cloud. That is about 500,000 kilograms or 1.1 million pounds (about 551 tons). Researchers have calculated that the average cumulus cloud weighs an incredible 500,000 kg (or 1.1 million pounds). About the weight of 100 elephants.

More Info: www.usgs.gov