On February 7, 1994, satellite images showed that Lake Superior had completely frozen over, although the lake’s center showed a very thin layer of ice that covered the water. The pictures appeared to settle the debate about whether the largest lake in the Great Lakes could ever completely freeze over.
Three consecutive days in which temperatures never broke 0 degrees combined with a 1.3-degree average daily temp in Marquette for January set the stage for a 50-day cold snap.
However, high winds the next day broke up the thin ice over the middle of the lake, quickly exposing open water.
Source: Michigan Every Day