How to Calculate The Distance of Lightning.

A thunderstorm is approaching, and suddenly you see lightning followed by a deafening clap of thunder. It sounded close really close. Calculating the distance from lighting can just give you peace of mind if you're in a safe location, or it can help you know if you need to find a safe path as soon as possible. So how close were you to the lightning strike? Read on to find out.
To calculate the distance from the lightning, as sound travels one kilometer every three seconds, divide the number of seconds by 3 for an answer in kilometers. The delay between when you see lightning and when you hear thunder occurs because sound travels much more slowly than light, therefore if you count 6 sec divide by 3 which equals 2 km.
To calculate in miles, likewise divide by 5. Therefore if you count 17 seconds / 5= 3.4 miles away.

Lightning -- Location Bundoora, Victoria, Australia 17-01-2014.