5The Sound of Thunder Travels at 1,225 Kilometers Per Hour
Thunder, the sound produced by lightning, travels at the speed of sound, which is approximately 1,225 kilometers per hour (761 miles per hour) in the air. Because sound travels much slower than light, there is often a delay between seeing a lightning flash and hearing the corresponding thunder. This delay can be used to estimate the distance of a lightning strike by counting the seconds between the flash and the thunder and then dividing by five to get the distance in miles (or dividing by three for kilometers).
