Dear Tom,
Does heat lightning really exist? I have heard that it’s either from a faraway storm or something else. What is correct?
Ben O’Dell, Shorewood, Ill.
Dear Ben,
Heat lighting truly exists, and your first suggestion is correct: Heat lighting is always lightning–normal lightning–produced by thunderstorms so far away from you that you cannot hear the lighting’s thunder. Lightning flashes often occur at thunderstorm tops 10-15 miles above ground. If there are no clouds between you and the cloud tops, as is frequently the case on warm summer evenings, the lightning can be visible across distances of 100 miles or more.
But lightning expert Ron Holle tells us that the sound waves of thunder rarely travel more than 15 miles and never more than 25, so we can often see distant lightning but not hear its thunder.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Place, Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
