Lakes Mendota, Monona and Wingra opened during the second week of April.
Lake Mendota officially froze Dec. 16 and opened April 12, for an ice season of 117 days, which is 12 days longer than the median duration.
Despite the persistent and sometimes brutal cold we experienced this winter in southern Wisconsin, the 117-day ice season pales in comparison to the record for Mendota, set in 1880-81, of 161 days. That’s nearly a month and a half longer than this year’s ice season.
Lake Monona froze Dec. 10 and opened April 10 for a season of 121 days, exceeding the median duration by 17 days.
Lake Wingra froze Nov. 27 and opened April 9 for a season of 133 days, also 17 days longer than the median.
Interestingly, the largest lake, Mendota, took only three more days to open than did the smallest lake, Wingra.
Because there is so much more water in Lake Mendota compared to Lake Wingra, the big lake froze 19 days later than the small lake. This testifies to the substantially larger amount of heat energy that must be removed from the larger Lake Mendota before it can finally freeze.
This energy is deposited in the overlying atmosphere where it can be used to make the lakeshore temperatures warmer than those at locations far from the lake. Such heat lost from the lake in late autumn, since it was originally deposited in the lake by sunlight during summer and fall, represents a delay in the transfer of energy from the summer-autumn sun to the wintertime air.