Lightning. Coloured historical artwork of a bolt of lightning striking a gas lamp in a street at night. Lightning occurs when a large electrical charge builds up in a cloud. This is probably due to the rapid movement of water droplets and ice particles within the cloud. Large thunderclouds generally have very turbulent interiors. The charge induces an opposite charge on the ground, and a few leader electrons" travel to the ground. When one makes contact, there is a huge backflow of energy up the path of the electron. This produces a bright flash of light and temperatures of up to 30,000 degrees Celsius."