Estimate storm distance using Lightning and Thunder -- Posted by inturi on Monday, September 21 2009
It is possible to calculate how far away a storm is by counting the seconds between a lightning flash and a thunder clap. Since it takes thunder about 5 seconds to travel 1 mile (3 seconds to travel 1 kilometer), simply divide the counted seconds by 5 to determine the miles (by 3 to determine the kilometers). Normally, thunder cannot be heard more than 20 miles (32 kilometers) away.