How often do the Great Lakes freeze?

January 29th, 2010 at 5:15 pm by under Weather

Most inland lakes freeze up every winter in Wisconsin. But how often do the Great Lakes freeze over? The answer depends on the lake. Lake Erie is a smaller and shallower lake which tends to ice over 7 out of every 10 winters. Meanwhile, Lake Ontario, which is furthest east, almost never freezes over. This is particularly due to its depth which drops to around 800 feet in some locations.
Chance Freezing
The data provided in the graphic above is based on winters dating back to the mid 70s.

Lake Michigan will only ice over 11% of our winters. In fact it hasn’t nearly frozen over since 1979. Since the lake has a north-south orientation the southern portions of the lake tend to stay warmer than the north.

As for Lake Superior, you wouldn’t think it could freeze over, but it happens. Superior is the largest fresh water lake in the world and contains more water than all of the other Great Lakes combined. It’s deepest point is around 1,300 feet. But still Superior freezes over… the last time it happened was last year. Take a look at the high resolution satellite image below and you can see that the lake is more than 90% covered with ice. The image is taken on March 1, 2009. Lakes tend to develop there most significant ice coverage during the month of February.
Superior last year
Compare that image to the satellite image taken last week of Lake Superior.

Superior This Year

As you can see, there is a lot of open water and the lake has barely began to freeze up. That is far behind where it was last year at this point. Last year, there was far more ice development. In other words, for Superior to freeze over this year it would require an extreme and extended cold blast during February.
Superior Last Year Now
While we have last year in mind. Take a look at the image below from Lake Michigan on January 27th. The bay of Green Bay is completely froze over and the bright reflectivity of the snowpack over the ice shows up well on this satellite image.
Michigan Last Jan
Meanwhile, this year the bay has recently froze up (as shown below), but the ice isn’t quite as thick. The thickest ice on the bay is in its southern and eastern sections. Most of the new ice has developed along the western portions of the bay.
Michigan Yesterday
All of the Great Lakes are behind average for this time of year when it comes to ice coverage. Mild temperatures during the past couple of weeks may be to blame. The region also hasn’t seen any extreme and long lived cold blasts. Thin ice is developing along the shores of most lakes, with the most ice coverage on Lake Erie.
current ice cov west

current ice cov east

As shown below, by March 1, Lake Erie could completely freeze over. Huron will see more ice development and in Lake Michigan more ice development is expected in the northern portions of the lake. Superior will develop more ice, but won’t be close to freezing over.

forecast ice east

forecast ice west

Until Next Time,
Meteorologist Andrew Thut

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