Dear Tom,
While watching a spectacular lightning display in a storm off in the distance, we noticed that most lightning seemed to be in the clouds. How many lightning bolts strike the ground? The Williamson family, Madison, Wis.
Dear Williamson family,
It is estimated that lightning strikes the ground 12-16 million times per year in the United States. As you have observed, however, many lightning bolts are not ground strikes-they occur as within-cloud or as cloud-to-cloud flashes.
Dr. Walter Lyons, who has closely studied lightning-strike data obtained from a network of lightning detectors in operation across much of the U.S. since the late 1980s, estimates that here in the Midwest, ground strikes represent only about 20 percent of the total number of lightning discharges produced by thunderstorms. In other words, about four intracloud lightning flashes occur for every ground strike.
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Tom Skilling is chief meteorologist at WGN-TV. His weather forecasts can be seen Monday through Friday on WGN News at noon and 9 p.m.
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