You can tell how far away a thunderstorm is by using the “Flash-to-Bang” method. Because light travels so much faster than sound, a simple formula makes all the conversions allowing you to use simple math to figure out the distance. When you see the flash of lightning, start counting “One-one thousand, two-one thousand,” etc. until you hear the distinct rumble or boom of thunder. Divide those seconds by five and you have the approximate distance, in miles, from the storm. (15 seconds, divided by 5 means the storm is 3 miles away!)