Lightning is a build up of electrons concentrating and discharging static electricity during a thunderstorm. As the thunderstorm develops, interactions of charged particles produce an intense electrical field within the cloud. A large positive charge is usually concentrated in the frozen upper layers of the cloud, and a large negative change, along with a smaller positive area, is found in the lower portions.

Thunder is the sound produced by explosive expansion of air super heated by a lightning stroke. When lightning is close by, the thunder sounds like a sharp crack. More distant strokes produce growling and rumbling noises. Because the speed of light is about a million times that of sound, a lightning bolt is seen before the sound of the thunder.