Stormii • Storm distance

A thunderstorm with lightnings and thunders can be a good spectacle to watch from home.
Suddenly you see a flash of lightning and wonder how far away it is, but... How do you calculate the distance of a thunderstorm?
Stormii will do it for you thanks to the fact that the distance of sound is slower than light. Knowing the seconds from lightning to thunder, Stormii tells you the distance of the thunderstorm.