File:Snow around the Great Lakes (MODIS 2019-12-25).jpg

English: It was beginning to look a lot like winter around the Great Lakes in late December 2019. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of the scene on December 22.

Broad cloud cover across the far northern (top) section of the image, including much of Lake Superior, suggests a potential storm, possibly dropping fresh snow, over parts of Ontario and Quebec, Canada. Snow covers most of the land in Canada and parts of the United States, especially southeast of Lake Erie and Lake Ontario. Starting from the northwest and moving counter clockwise, the lakes are: Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario. Lake Erie is colored with blues and greens from the remnants of a late fall bloom of phytoplankton, which are microscopic plant-like organisms that grow in huge numbers when conditions are favorable.

Despite the winter weather, and the chill required to allow snow to lay on the ground, the waters of all the lakes have no obvious ice forming on them. Indeed, the National Weather Service reports little ice on the Great Lakes, with only very small amounts reported forming along the shores of the Canadian side of some of the lakes by December 23.

Large lakes, like the Great Lakes, rarely freeze over, even in extended below-freezing weather. This is largely due to the effects of winds, which destroy the continuity of ice cover, breaking the forming ice and moving it along the water.

According to the National Oceanic and Atmospheric Administration (NOAA), the seasonal evolution of ice cover on all of the Great Lakes follows a relatively consistent schedule. All of the lakes begin to see ice develop along the shallower coasts during late fall and early winter before ice begins to expand in coverage from north to south across the Lakes throughout the winter. The Great Lakes farther south (Erie and Ontario) see their maximum ice extent in February while the maximum ice extent is normally found in March in the northern Great Lakes (Superior and Huron). By April, the lakes begin their annual melt.