What are thunder and lightning?

The sky goes dark, a bright flash zigzags down, and then — BOOM! A storm can feel exciting and a little scary. But where do the flash and the bang come from?

Clouds get charged up

High inside a big storm cloud, tiny bits of ice and water are tossed up and down by the wind. They bump and rub against each other again and again. All that rubbing builds up something called electric charge, just like when you rub a balloon on your hair and it crackles.

The cloud fills up with more and more charge until it simply cannot hold any more.

Lightning is a giant spark

When the cloud is too full, all that charge jumps free in one huge spark. That spark is lightning! It leaps between the cloud and the ground, or from cloud to cloud, in a blink. Lightning is so hot it shines brighter than the sun.

Thunder is the big BOOM

The lightning heats the air around it incredibly fast. The air puffs out so quickly that it makes a loud bang — that bang is thunder.

You always see the flash before you hear the boom. That is because light travels faster than sound, so the light reaches your eyes first.

Wonder fact: Count the seconds between the flash and the boom — every 3 seconds means the storm is about 1 kilometre away!