An unseasonably mild weather pattern for much of the winter season has put a limit on the amount of ice that has been able to form on many of the Great Lakes. The Lake Michigan/Huron is no exception to this due to the relatively mild temperatures leading to above average water temperatures.
The graphic above shows ice coverage for portions of Lake Michigan and for Lake Superior. The dark gray and black shading indicate the median ice concentration. Areas of the lower bay of Green Bay are showing almost full ice coverage, but the further north of the bay you go and especially into Lake Michigan the ice concentration is very low.
This graph indicates the ice coverage on Lake Michigan which is reported daily. The red line shows the concentration of ice on the lake where the blue line is the average ice coverage for that time of the year during the period of 1973-2019. After a seasonal or slightly above seasonal start to the ice coverage during the first half of December we have seen a stretch of below average ice coverage on Lake Michigan since.
As of Wednesday morning the total ice coverage on Lake Michigan was 6.6%. For the entire Great Lakes system as of Tuesday ice coverage was only at 5.6% which is also well below the seasonal average.
One of the reasons, as earlier mentioned, for the lack of ice on Lake Michigan is due to the surface water temperatures that have been above average for most of the winter season not just in Wisconsin, but through much of the Great Lakes region and Midwest. The graph above tracks the average temperature of the surface water on Lake Michigan measured in degrees Celsius. The blue line indicates the average surface water temperature of Lake Michigan throughout the year from the 1992-2019 time period. You can see that so far this year the red line has been above the seasonal average.
Here is a similar graph of surface water temperatures in Lake Michigan, but we also add in the water temperatures throughout the last five years. The current temperature for 2020 is shown in the black line. You can see that the current water temperatures this year are near the top of the last five years.
Temperatures since December 1st on last have been above average across the entire state as indicated by the yellow and orange shadings.
Temperatures across most of the region will remain above average the rest of the month and into the early portions of February. The Climate Prediction Center 8-14 day outlook which will take us into the middle portions of February indicates a chance for below average temperatures across the western Great Lakes. Average highs in Green Bay by that time of the year will be in the upper 20s.
The five day forecast for ice coverage shows some increase in ice across the northern portions of Lake Michigan bringing the mean concentration to 7.2% on the lake. This will still be below average for that time of the year.