=Answer= When warm, moist air rises very quickly, deep cumulonibus storm clouds form. Ice crystals and water droplets whirl around inside the clouds and bump into each other, making tiny electric charges. The charges build up until huge electric sparks flash from cloud to cloud or down to the ground and back. The lightning flash heats up the air as it passes. The air expands very rapidly and makes the booming noise we call thunder. Hope this helps.