In any given year, the formation, movement, and timing of ice cover on the Great Lakes is temperamental—changing substantially with shifts in weather and climate patterns. The 2020-2021 winter season fit that profile, as wild swings in the weather took Great Lakes ice on a wild ride. Interestingly, the maximum ice cover this year was near the 1973-2020 average of 53 percent, according to Jia Wang, an ice climatologist at NOAA’s Great Lakes Environmental Research Laboratory. According to Wang, air temperatures are the main factor affecting ice cover on the Great Lakes. The highest maximum ice cover (94.7 percent) on record occurred in 1979, and the lowest maximum (11.9 percent) occurred in 2002.