Think you could lift a cloud? Think again. Clouds are tiny droplets of liquid or frozen water suspended in air. Meteorologists measure the weight of the water in clouds in terms of grams per cubic meter (g/m3). It varies by cloud type: A fluffy cumulus cloud contains 0.2 to 0.5 g/m3 of water; a cumulonimbus (thunderhead) might have 15 g/m3. A modest fair-weather cumulus cloud of one cubic kilometer in volume (about 0.24 cubic miles) contains at least 200,000 kg, or 220 tons of water. And the air in a cloud that size weighs even more: 1.2 billion kg, or 1,320 tons. So how do clouds even stay up? The secret is the size of the drops and the strength of the updraft. Typical drops are so small (0.01 mm) that the slightest updraft keeps them aloft.
Source: NOAA, National Weather Service