You can measure a winter in many ways: temperature records, snow cover, even travel delays. But to truly see how frigid this winter has been—at least for the eastern half of the U.S.—you need to go way up. Satellite imagery shows that an incredible 88% of the Great Lakes—Superior, Michigan, Huron, Ontario and Erie—are now frozen over. That’s the largest ice cover the Great Lakes have experienced since 1994, and it means that there is an astounding 82,940 sq. miles (214,814 sq. km) of ice covering the biggest collection of fresh water in the world.
How unusual is this? Since 1973, the average maximum ice cover extent for the Great Lakes has been just 50%, and in those four decades, the ice extent has surpassed 80% just five times. (In 2002, just 9.5% of the Great Lakes froze over during the winter, the lowest extent on record, while the greatest extent was 94.7% in 1979.) And no lake is as iced over as Superior, where the extent is 95.3%.