All thunderstorms have one thing in common — lightning! We can use lighting and the sound that is makes, thunder, to tell how far away a thunderstorm is from you!
Sound travels at 340 m/s… this breaks down to about 1 mile for every 5 seconds. Since light travels so fast the moment you see lightning is the moment that it’s actually happening. The sound will take a little while to reach your ears. We can calculate the distance the sound is traveling by counting the seconds that it takes for the sound to reach you.
The moment you see lightning, start counting! Every 5 seconds is equal to 1 mile away. If it takes 10 seconds, it’s 2 mile away. 20 seconds, 4 miles! You can repeat the experiment with the same storm a little while later and see if it’s moving toward you or away from you.