Book 7, Question 1
Why Do Clouds Form in the Sky?
A cloud is not a puffy pillow. It is billions of tiny water droplets floating together. The air around you always holds invisible water, called water vapor.
From the book
Page from A Million Whys Book 7
More fun facts
- Every cloud droplet has a tiny speck of dust, dirt, smoke or sea salt at its center.
- These specks are called cloud condensation nuclei. Water vapor needs them to turn into droplets.
- The specks are only about one hundredth the size of the cloud droplet that forms around them.
- Even with its speck in the middle, a cloud droplet is still almost pure water.
- A cloud can weigh tens of millions of tons and still float in the sky.
- Winds can carry clouds along at up to 150 miles per hour.
Sources: NOAA, NOAA, NASA Science
Questions kids ask
Is there dirt in clouds?
Yes. Every cloud droplet forms around a tiny speck of dust, smoke or sea salt.
How heavy is a cloud?
A cloud can weigh tens of millions of tons, even while it floats.