Falling Rain T e water droplets inside a cloud are so small and light, they fl oat. But if they combine, they can bring rain. Small droplets bump into larger droplets. T ese droplets join together. When a droplet becomes too heavy to fl oat, it falls from the cloud as rain. T is is called precipitation. Precipitation soaks into the ground.
It fi lls rivers, lakes, and the ocean. T en the water cycle continues. Rain is not the only kind of precipitation that falls from clouds. Snow, sleet, and hail come from clouds, too.
Low and High Clouds Even though clouds form in similar ways, they don’t all look alike. T at’s because height, location, and other factors can aff ect how a cloud looks. One kind of cloud forms so close
to the ground, you can walk through it. It’s fog! Stratus clouds form low in the sky. T ey look like fuzzy gray blankets that stretch across the sky. Other clouds form high above Earth. Cirrus clouds are made of ice crystals. High winds tear them into thin wisps.
Is it a UFO or a Cloud? Height is only one factor in how a cloud forms and looks. Winds also play a big role. Winds push clouds across the sky. T ey swirl clouds into diff erent shapes. Imagine clouds in the shape of
a UFO. I saw one once in Austria. A bitter wind was blowing. I saw a giant shape hovering over my head. It had a smooth surface and a round shape. It looked like it was hovering. It made me think of a fl ying saucer.
How the Cloud Formed I later learned that the wind and the mountain helped shape that cloud. First, the wind slammed into the mountain. T e wind shot upward, over the mountain. T en the wind sank. T is sudden change made the wind wobble like a wave. T e wave made water vapor in
the air bounce up and down, too. At the top of the wave, the air was cool enough to condense, or turn into water droplets. As a result, a cloud that looks like a smooth disc formed. To some, it looks like a UFO!
20 NATIONAL GEOGRAPHIC EXPLORER
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