Image Credit: National Oceanic and Atmospheric Administration (NOAA)

In massive storm clouds, the friction between large particles composed of many atoms builds up a large separation of electric charge, and creates voltages approaching 100 million volts. With such a big voltage, things can get explosive and the energy is released as a lightning bolt. Any time there is an electrical current, there is also heat associated with the current. Since there is an enormous amount of current in a lightning strike, there is also an enormous amount of heat. In fact, a bolt of lightning is hotter than the surface of the sun. This heat is the actual cause of the brilliant white-blue flash that we see.

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