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This question asks me to predict the future, which is one skill I’m less than adept at. (If I were omniscient, I might’ve done the Rushmore crew a favor and gotten a haircut.) But because the good folks in the Department of Atmospheric and Oceanic Sciences (AOS) have helped to make Lake Mendota the most studied lake in North America, I can at least give you an informed guess. In fact, it’s likely that the lake will be thawed by the time you read this. How’s that for omniscient?

The university has been recording the ice cover on Lake Mendota since the spring of 1853, which, if you’ve done your homework, you know is just four years after the UW held its first class. The ice thawed on April 5 that year, opening the lake to navigation.

The next couple of years had sporadic records, but beginning in the winter of 1855–56, the date of each winter’s freeze and spring’s thaw is faithfully put down. The UW now has some 160 years of data, all of which are posted online.

These data show that Lake Mendota has a median duration of ice cover of 105 days. The longest stretch of ice was the winter of 1880–80 (161 days — more than five months!), and the shortest was just three weeks in 2001–02.

How does AOS determine when the lake is frozen and when it’s thawed? After all, it’s a big lake, and freezing is a gradual process. “There is some question how scientific the dates have been arrived at over the years,” writes Lyle Anderson ’68, MMusic’77, an AOS associate and manager of Wisconsin’s State Climatology Office, in an online post. “Our vantage point on the thirteenth floor of the Atmospheric and Space Sciences Building … does provide a fair view of the three lakes. However, closer inspection of the lakes from various vantage points is made.” (Lyle is a bit of a Renaissance man — he also plays the bells in the carillon tower. Evidently, he likes tall buildings.)

This year, climatologists noted a strong El Niño current in the Pacific, which resulted in a mild winter. The last strong El Niño years were 1982–83 and 1997–98. In the former, Lake Mendota had 54 days of ice cover and opened March 8; the latter had 47 days and opened February 27.

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