How to Find the Distance of a Storm
- 1). Wait for a lightning flash to appear in the storm. Start your stopwatch the instant you see one.
- 2). Listen carefully for the thunderclap. Stop the stopwatch as soon as you hear it.
- 3). Convert the time between lightning flash and thunderclap from seconds to hours by dividing the seconds on the stopwatch by 3600 (the number of seconds in an hour) on your calculator. For example, if you counted 10 seconds between lightning and thunder, you would divide 10 by 3600 to get 0.00278.
- 4). Multiply the resulting number by 750 to determine the distance in miles to the storm cloud. The speed of sound at the altitude of storm clouds is about 750 miles per hour. The formula distance = rate x time tells you that multiplying the speed of sound by the time it took the sound to arrive gives you the distance to the source of the sound (in this case, the storm cloud where the lightning originated). If the time difference was 10 seconds, multiply 0.00278 by 750 to get the distance: 2.08 miles.
Source...