What are clouds made of?

Clouds are made up of billions of minute water droplets and microscopic ice crystals that float in the sky together. A cloud's droplets are around 100 times smaller than a raindrop. Low-level clouds, or those less than 6,000 feet (1,800 meters) above the earth, are largely formed of water droplets. They can, however, contain microscopic snow and ice crystals in cold conditions. During the summer, mid-level clouds, or those between 6,000 and 20,000 feet (approximately 6,000 meters), are made up of water droplets, but during the winter, they have a significant concentration of ice crystals.

Above 20,000 feet, high-level clouds are mostly comprised of ice crystals. Many clouds, in addition to holding water and ice crystals, include minor amounts of solid particles such as smoke and dust. The majority of the water in clouds is in the form of extremely minute droplets. The droplets are so light that they float through the air. These droplets may merge with other drops. Then they grow into bigger drops. When this happens, gravity pulls them down to Earth.