Hey Ray: The Science Behind The Distance Of Thunderstorms

PITTSBURGH (KDKA) -- When it comes to thunderstorms, can you really tell how far away a storm is by counting the seconds between the flash of lightning and the rumble of thunder?

The answer is yes, but there's a little more to it.

First of all, thunder is caused by lightning's incredible heat. When lightning happens in a storm, it causes the air next to the bolt to almost instantly heat up to as high as 50,000 degrees.

Yeah, five times hotter than the surface of the sun.

Right after the flash, the air cools almost as quickly, so the heat causes a big quick expansion. Then the cooling causes the air to contract quickly, creating a thunderous soundwave.

Since light travels at 186,000 miles per second, you see the flash from the lightning almost instantly. The sound is a little slower. It takes under five seconds to travel a mile.

Here's an example: if lightning and thunder were in a race, the lightning would finish instantly, whereas it would take thunder a lot longer to get to the finish line so that we can hear it.

Since we know it takes five seconds to travel one mile, if you count the seconds between the flash and the boom and divide that by five, you can tell how far away the thunderstorm actually is.

No matter how far away you are from a storm, if you can hear thunder, you're close enough to be struck by lightning. So when thunder roars, get indoors.