Simulated lightning strike to a sailboat model in a lab.Lightning occurs when a large electrical charge builds up in a cloud, probably due to the friction of water and ice particles. 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.