Why Does It Rain?

WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

All around you, in the air you breathe and in the sky above you, water hangs out in a form called vapor (VAY-purr). The amount of water vapor in the air is called humidity (hu-MID-it-ee). Every cloud in the sky is made from this vapor, from the big white fluffy ones to the dark gray heavy ones. These are the ones that rain.

Warm air can hold more water vapor than cold air. Warm air also rises, or goes up. And cold air can push warm air up. As these tiny drops of water fly high into the sky, they gather together in clumps and form clouds.

When enough of this water vapor gathers together in a cloud and then cools down, it gets very heavy and forms droplets called condensation (CON-den-SAY-shun). This is when gravity takes over. Gravity is the force that holds you, your house, and all the animals onto the Earth so we don’t float off into space. With clouds, gravity pulls the water droplets out of the sky, and they fall as rain. If the air is cold enough, those raindrops can become ice crystals. Then they fall as snow, sleet, or hail instead of rain. 

To learn more about rain, visit Easy Science for Kids.