How do clouds form, and what do different clouds tell us about the weather?

Why do some clouds look like cotton balls while others look like flying saucers? The shapes of clouds reveal different things about changing weather patterns.
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How to tell how far away lightning is by counting

Lightning flashes from a thunderstorm light up the landscape in eastern Brandenburg. (Photo by Patrick Pleul/picture alliance via Getty Images) When thunder rumbles in the distance, there's a quick ...