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Lightning. Bolts of cloud-to-cloud and cloud-to- ground lightning. The unusual colour of the night sky is caused by dust particles thrown into the air by a dust storm. Lightning occurs when a large electrical charge builds up in a cloud, probably due to the rapid movement of water droplets and ice particles in its turbulent interior. The charge induces an opposite charge in a nearby cloud, or is attracted to the oppositely-charged ground, and a few leader electrons travel from one to the other. When one makes contact, there is a huge backflow of energy along the path of the electron. This produces a bright flash of light and temperatures of up to 30,000 degrees Celsius. (KEYSTONE/SCIENCE PHOTO LIBRARY/JIM REED) === ===