Things You'll Need
Instructions
Begin counting seconds immediately after observing a flash of lightning. It takes about one second to say four syllables, so count by saying "One thousand one, one thousand two ..." Alternatively, use a stopwatch.
Stop counting when you hear the thunderclap. The more distant the lightning, the less like a "Boom!" the thunder will sound.
Divide the number of seconds counted between lightning and thunder by 5. The result is an approximate distance, in miles, to the lightning bolt.