Why are clouds white?

Remember how sunlight has every colour mixed inside it? The tiny bits in the air bounce blue around the most. Cloud drops are much bigger, so they bounce every colour about the same. All the colours mixed together look white, so the cloud looks white too.

Then why are rain clouds grey?

Rain clouds have bigger drops, and big drops bounce even more light around. So less sunlight makes it all the way down to the bottom of the cloud. From underneath, you're looking at that dim bottom, so it looks grey.

What are clouds made of?

Roo answers for ages 4–10, then goes 2 steps deeper each time a child asks why.

Roo says

Water from puddles and rivers floats up into the air as a gas, too tiny to see. High in the sky, the air is cooler. There, the water gathers into tiny drops on specks of dust. The drops are so light they float, and lots of them together make a cloud.

For ages 4–7

Checked against What are clouds? (NASA)
Why are clouds white?

Remember how sunlight has every colour mixed inside it? The tiny bits in the air bounce blue around the most. Cloud drops are much bigger, so they bounce every colour about the same. All the colours mixed together look white, so the cloud looks white too.

For ages 6–9

Checked against Why are clouds white? (Met Office)
Then why are rain clouds grey?

Rain clouds have bigger drops, and big drops bounce even more light around. So less sunlight makes it all the way down to the bottom of the cloud. From underneath, you're looking at that dim bottom, so it looks grey.

For ages 7–10

Checked against Why are clouds white? (Met Office)