Look up at the sky. What are clouds made of? Let's find out.

Clouds are made of tiny drops of water. Or they are made of tiny bits of ice. Clouds look white because sunlight is white.

Cumulus clouds are puffy. They often show up on sunny days. Some grow into storm clouds.

Cirrus clouds are thin clouds high in the sky. They are made of bits of ice.

Stratus clouds are low and gray. They can cover the whole sky like a blanket. They give light rain or light snow, if any.

Rain and snow fall out of clouds. Dark gray clouds bring steady rain or snow.

Look for white streaks behind high-flying jets. They are clouds called contrails.

Lenticular clouds often look like flying saucers. They are shaped like a lens.

Some clouds are thunderclouds. Thunder is the sound that lightning makes.

You see lightning before you hear its thunder. That is because light travels faster than sound.

When you hear thunder, go indoors. Go into a building or a car with a roof.

Words to know

• stratus: low cloud
• cirrus: thin cloud
• contrails: jet clouds
• lightning: sky flash