For those of us who have ever wondered why rain falls from the sky, the answer is both simple and complex. Rain is the result of two main factors: warm air and cold air. When warm air rises, it leaves an area of low pressure behind. Cold air rushes in to fill the void and as it does so, it picks up moisture from the ground. This moisture condenses into clouds and eventually falls back to Earth as rain.
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But why do thunderstorms form? The answer has to do with something called a cumulonimbus cloud. This is a large, fluffy cloud that can extend up to 60,000 feet into the atmosphere. It is made up of water droplets and ice crystals that are constantly rising and falling. As they rise, they cool and condense into water droplets. As they fall, they warm up and evaporate.