Launching weather balloon with field mills into storm. Balloon is 1500 cubic feet surplus nylon with fins that is tethered and carries an electronic field meter. Langmuir Atmospheric Research Lab on Mt. Baldy, New Mexico (1992) 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.