Cloud droplets are extremely small. They are about ten thousandth of an inch across, a thousand times smaller than a raindrop.

The biggest clouds are cumulonimbus, climbing up to 9.7 kilometers (6 miles) high and holding up to half a million tons of water.

Sunbathing on sunny days with clouds in the sky can be dangerous.

Clouds can reflect so much ultraviolet light from the sunlight they dramatically increase the ultraviolet reaching the ground.