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How Far Away Is That Storm?

Did you know that you can figure out how far you are from a storm by watching lightning and listening for thunder?

Lightning is over 40,000 degrees Fahrenheit. A bolt of lightning heats the air along its path causing it to expand rapidly. Thunder is the sound caused by the rapidly expanding atmosphere. The light and sound actually happen at the same time, but the light of the lightning flash travels faster than the grumbling sound of the thunder. The time between the flash of light and thunder will tell you how far you are from where the lightning struck.

What you will need:

  • A thunderstorm
  • A stopwatch (or the ability to say, "One-Mississippi, Two-Mississippi...")
  • A safe indoor location

Make it happen:

  1. After you see a flash of lightning, count the number of seconds until you hear the thunder. (Use the stop watch or count "One-Mississippi, Two-Mississippi, Three-Mississippi," etc.)
  2. For every 5 seconds the storm is one mile away. Divide the number of seconds you count by 5 to get the number of miles.

What's Happening?

What travels more quickly, light or sound?

If you said light travels faster than sound, you're right! The lightning and thunder are happening at the same time, but light reaches you instantly, while sound takes longer.

Do you ever see lightning without hearing thunder? Some call that "heat lightning," but it is really lightning that is over 15 miles away and too far away for you to hear the thunder!

LOOK OUT if you see the lightning and hear the thunder at the same time!

Do you need to review the Storm Safety page?


More activities to try: