Thunder facts for kids
When lightning is very near, thunder will be heard soon after the lightning flash, and the sound will be very loud. If the lightning is farther away, the thunder will be a few seconds or many seconds after the lightning. People can guess how far away the lightning is by counting the number of seconds between the time they see the lightning and hear the thunder.
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Thunder is the sound produced by lightning.
Thunder Facts for Kids. Kiddle Encyclopedia.