Estimate Distance to Lightning

Lightning is amazing. By using your observation skills, you can figure out how far away lightning is, a fun activity on a stormy night.

What you need

• A thunderstorm

• A safe place to watch from

Watching lightning

Lightning is amazing to watch. The fierce electrical lightning bolts look and sound spectacular, often accompanied by rain and wind. On a stormy night, it’s fun to watch a storm and marvel at the power of the sky.

To figure out how far away a lightning strike is, you just need to watch and listen. The steps are simple: once you see a lightning bolt, start counting seconds. When you hear the thunder from that lightning bolt, stop counting. For each five seconds that pass, the lighting is a mile away. So if you count to ten before hearing thunder, the lightning struck about two miles away.

Of course, sometimes lightning is too far away to hear. And when there’s a lot of lightning, it can be difficult to listen for the right thunder.

But for the other times, just remember: 5 seconds = 1 mile.

Direction and distance

Seeing a lightning bolt tells you its direction. Counting the seconds until you hear the thunder tells you its distance. Once you know both direction and distance, you can estimate the location. So get out a map and take a look. What do you think the lightning hit?

Lightning photos

When it comes to lighting, there’s no replacement for watching a storm yourself and hearing thunder crash over you. Just remember the saying: “When thunder roars, stay indoors.” In other words, when a storm arrives, make sure you’re safely indoors.

If there’s no storm today, just look through the photos below. (You’ll have to imagine the rain, wind, and thunder yourself!)

Why does five seconds correspond to a mile?

Why does the “5 seconds = 1 mile” rule work? To understand, you just need to think about the speed of light (which determines when you see the lightning) and the speed of sound (which determines when you hear it).

Light is astoundingly fast. It travels at 300,000,000 meters per second. Over short distances, it is basically instantaneous, so you don’t need to worry about it. Essentially, you see the lightning when it happens.

As for sound, it’s a lot slower. Sound travels at about 330 to 340 meters per second, which is about one fifth of a mile per second. This means that the sound of thunder takes about five seconds to travel a mile.

Violà! For every mile that thunder has to travel, it takes five seconds.

With this information at your disposal, you can estimate the distance to lightning. On the next stormy night, sit by the window and figure out where lightning strikes!