Air Date: Week of August 18, 2000

This week, facts about thunderstorms. August is prime thunderstorm season – at any given moment 1800 storms are underway on Earth.

Transcript

CURWOOD: It's Living on Earth. I'm Steve Curwood

(Thunderclap and rain)

CURWOOD: At any given time there are more than 1,800 thunderstorms underway on Earth. And in the U.S., August is prime thunderstorm season. Warm, humid, and unstable air is the key ingredient for thunderstorms. When water drops are rapidly agitated in the storm cloud, molecules get stripped of electrons, giving them a positive charge. Meanwhile, the ground has plenty of electrons and a negative charge. Opposites attract, and sooner or later the charge in the clouds builds up so much that a giant spark flies to the ground, and we call it lightning. Heat from the lightning bolt causes the air around it to expand explosively, which we hear as thunder. You can tell how far you are from the storm cell by counting the seconds between the lightning and the thunder. Sound travels slower than light, so every five seconds between lightning and thunder corresponds to about a mile from the lightning bolt. If you're outside during a thunderstorm, it bears repeating: Stay far away from that tall tree. Taking shelter under a tree is still the main reason for 100 lightning deaths each year in the U.S. A car is a safer bet, unless it's a convertible. The metal body should direct the charge away from the occupants. By the way, lightning does strike the same place more than once, contrary to popular belief. It hit Ray Sullivan, a park ranger, seven times between 1942 and 1976. And for this week, that's the Living on Earth Almanac.