Sat. AM update. (1/22) – Great Lakes ice cover is currently well below average (so far, this month of January is averaging 6.5° warmer than average in G.R.). These numbers for each Great Lake and Lake St. Clair are computed for each day of the winter. There is a record of daily ice cover on the Great Lakes going back to 1973.
Ice cover fell from 11.5% on Friday 1/18 to 7.8% on Friday 1/24. That’s mostly because strong winds broke up some of the ice. When the winds go light/calm, and when it gets colder, then ice will reform. The average % of ice cover on the Great Lakes for Jan. 25 is 25%.
The greatest ice extent on the Great Lakes was 94.7% on Feb. 19, 1979 (toward the end of the third cold winter in a row). The least maximum ice extent for any day during the winter was 11.9% on Mar. 7, 2002. Last year, the maximum Great Lakes ice cover was 80.1% on Mar. 9, 2019 – the 7th highest extent since 1973. We have had above average ice cover on the Great Lakes in four of the last six winters. The Coast Guard icebreakers were busy in the winters of 2013-15 and 2017-19.
On the graph above, you can see the high ice extent in the late 1970s – after the coldest 3 consecutive winters in G.R. history. You can also see the low ice extent following the really warm El Nino of 1998.