Question: What causes lightening?

Karen Reed answered on 18 Jun 2012:

Hiya Meg,

lightening is a bolt of electricity flowing between a cloud and earth – or between two clouds. As it travels inthe air it heats it up soo much it glows white hot – which is what we see as lightning.

Clouds can become charged due to the movement of the particles inside them – they rub against each other stripping off electrons and causing static electricity – much the same as you do when you rub a balloon up agains you hair of a fluffy jumper.

The charge then builds up and seperates out in the cloud so there is a positive side and a negative side.
If the difference in the charge between the bottom of the cloud and the earth (or things on the earth) is big enough, then electrons want to flow between the cloud and the earth. when they do you see the lightning bolt (electricity) flow between the cloud and the earth – this is the lightning.