Has Lake Michigan ever been totally frozen?
— Jim Penning, Oak Park
It has not. Ice development on Lake Michigan, usually beginning in January, attains its maximum extent by early March.
Wind and wave action, combined with the vast reservoir of heat contained in the lake, prevents it from freezing completely.
According to Environment Canada and the U.S. National Weather Service, lake ice coverage reached 90 percent to 95 percent in the winters of 1903-04, 1976-77 and 1978-79.
Data indicate that three of the Great Lakes (Superior, Huron and Erie) have totally frozen over in a few of the very harshest winters since 1900, but Michigan and Ontario have never achieved complete ice coverage.