Dear Tom,
My wife and I are having a disagreement as to what comes first: thunder or lightning. There is a lot riding on your answer.
— Bill and Maureen Lahtinen, Elk Grove Village
Dear Bill and Maureen,
Lightning always occurs first — always — because lightning causes thunder.
The electric spark that constitutes a lightning bolt heats the air through which it passes to at least 50,000 degrees in thousandths of a second. Explosive expansion of the air immediately occurs, followed by cooling and sudden contraction. These events trigger waves in the air which we interpret as thunder. The initial thunder that you hear comes from the point on the lightning channel closest to you; the last sound comes from the most distant point.
It would be difficult, probably impossible, to pair each lightning discharge with the thunder that it produces.
———-
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or: asktomwhy@wgntv.com
Weather Report is prepared by the WGN-TV Weather Center, where Tom Skilling is chief meteorologist. His forecasts can be seen Monday through Friday on WGN News at noon, 5:55 p.m. and 9 p.m.
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