Has Lake Michigan ever completely frozen over in the winter?
—Henry Cook, Berwyn
In records dating from the middle 1800s, even in the coldest winters, Lake Michigan has never completely frozen over. It has been as much as 90 percent or more ice-covered in 1903-04, 1976-77, 1978-79, 1998-99 and 2013-14, but the lake is a massive reservoir of heat that is released only slowly into the air. Constant wind and wave action further inhibits the formation of ice. Less than half the lake freezes over in an average winter. The lake extends more than 300 miles from north to south and most of the open water is in the south part of the lake, where the chill is less severe. Lake Erie, the shallowest of the Great Lakes, is the only one that occasionally freezes completely.