Image caption
Percent ice cover on the Great Lakes at winter maximum each year since 1973. The dashed line shows the long-term average of 51%. Prior to the mid-1990s, most years were above the long-term average; since then, most years have been below average. As of February 13, 2014, the lakes were 88% ice covered. Graph adapted by NOAA Climate.gov, from an original provided by The Great Lakes Environmental Research Lab.