What are clouds made of?

The question "What are clouds made of?" comes from Ms. Thelen’s class.

Summer brings bright, blue skies and white, fluffy clouds in all shapes and sizes. Clouds can even be dense enough to cast a shadow on the ground! What are clouds made of?

Clouds are made of water. Water enters the atmosphere when the sun heats up bodies of water, such as lakes and rivers. The water becomes water vapor and rises into the atmosphere, kind of like boiling a pot of water and watching the steam rise. Hot air rises, so the water vapor is carried high into the sky, where the temperature eventually cools.

At the cooler temperatures, water vapor interacts with tiny particles of dust and dirt in the air to condense into tiny water droplets. It’s like when your cold glass ends up covered in water on a hot day, but the drops are much smaller. When the water droplets in the air get big enough, they start sticking to other droplets to form clouds. Eventually, the water droplets get so big that they fall from the clouds as rain.

Fun fact: If a cloud forms really high in the atmosphere, the water droplets freeze, and the cloud will be made of ice crystals instead of water droplets.

Ronnie LaCombe is a graduate student at the University of Missouri studying biology.