Why does it rain?

Splish, splash! Where does all that rain come from, falling out of the sky? Believe it or not, a lot of it used to be water in puddles, rivers and the sea. It went on an amazing journey up and back down again.

Water floats up into the air

When the Sun warms water, some of it turns into an invisible gas called water vapour and floats up into the sky. This is called evaporation. You can’t see it, but the air is carrying water up high.

Up high it makes clouds

The higher the vapour rises, the cooler the air becomes. Cool air makes the vapour turn back into teeny-tiny water droplets. Billions of these floating droplets clump together to make a cloud.

Droplets grow heavy and fall

Inside the cloud, the little droplets bump and join into bigger and bigger drops. When a drop gets too heavy for the air to hold, down it falls as rain.

The rain soaks into the ground and trickles back to the rivers and sea, ready for the Sun to lift it up all over again. Round and round it goes!

Wonder fact: A single fluffy rain cloud can hold more water than a huge passenger plane weighs — but it floats because the droplets are so tiny and spread out.