WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.

How big is Lake Michigan and how does it affect the weather?

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Dear Tom,
How big is Lake Michigan and how does it affect the weather?

Janet
 
Dear Janet,
Lake Michigan is the third largest Great Lake (after Superior and Huron) and the world's sixth largest freshwater lake.  It boasts more than 1,600 miles of shoreline and covers more than 22,000 square miles. It is more than 300 miles long and nearly 120 miles wide. The average depth is about 280 feet and its deepest part (925 feet) is mid-lake east of Manitowoc and Two Rivers, Wis. The lake has a great deal of influence on the surrounding area's weather. Among the most important; it keeps areas near the lake cooler in summer and warmer in winter, extending the growing season by several weeks as compared to inland areas. It causes more cloudiness and generates both lake effect rain and snow in the cold season but often suppresses thunderstorm development in the warm season.