Some of the largest negative temperature anomalies (departure from average) in the Northern Hemisphere this winter have been near the Great Lakes. Therefore, it is no surprise that ice coverage on the five Great Lakes is very high this winter. The five lakes combined were 87% ice covered as of last Friday.
That was the highest level since February of 1996. Lake Superior is almost completely frozen over with 95% ice coverage. It was near that point in March, 2009, but the last time the lake was considered 100% ice covered was in March, 1996. Lake Huron is also almost completely iced over with 95% coverage, Lake Michigan was at 80% coverage and Lake Erie was 96% frozen over as of last Friday. Although Lake Ontario is the smallest of the five Great Lakes in size, it has three times the volume of Lake Erie, meaning it is a much deeper lake and harder to freeze.
That is one reason why Lake Ontario has the lowest ice coverage this winter with just 33% of that lake frozen over.