Dear Tom,
Now that the weather has gotten hot why has Lake Michigan turned so chilly?
–Mehul Jethva, Joyce and Ted Husak and Brett Konken
Dear readers,
It seems counterintuitive, but when the city turns hot, Lake Michigan water temperatures usually drop. A process called upwelling is to blame. As the lake warms during the summer the sun’s rays heat the water closest to the surface while the deeper water remains cold. Hot weather arrives in the city on brisk south and southwest winds that push the warm surface water out into the lake toward the east shore, allowing the colder bottom water to upwell and replace it. As a result, between Aug. 7 and Aug. 10, Chicago’s shore water temperature dropped to 63 degrees from 71 degrees while the water at Michigan City, Ind., jumped to 67 degrees from 55.
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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 11:30 a.m., 5:30 p.m. and 9 p.m.
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