between the thunder and the lightning and it's less than 30 seconds or so, the lightning is closer than five miles or so. it's time to take cover. >> reporter: so less than 30 seconds between thunder and lightning means that next lightning strike could be less than five miles away. if you'd like to learn more, tune in to the national geographic channel for "lightning chasers." it premieres this thursday. david muir, abc news, new york. >> stay in the house. >> fascinating. at any given time over 2,000 thunderstorms are taking place somewhere on the earth. isn't that amazing? >> your chance of being struck by lightning, 1 in 6,250. so -- >> i love that lightning can create natural glass. if it strikes the sand in the right way it can create a little bit of glass. >> that's crazy. >> mother nature. don't mess with mother nature. let her do her thing. >> absolutely. when we come back, christiane amanpour has taken