Lightning demonstration strikes model house and church with impulses of up to 800,000 volts. Deutsches Museum, Munich, Germany. 1991..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.