Where Does Lake Mendota’s Freeze Date Fall in Historic Average?

In case you missed the news, Lake Mendota was officially deemed “frozen” by the Wisconsin State Climatology Office on Sunday. That January 3rd “ice on” date is about two weeks later than the median freeze date of December 20th, although it’s a far cry from the record late-freeze date of January 30th in 1932. This January freeze is also an indicator that the days of December freezes may be moving towards something that’s only talked about in historical terms.

You see, folks in Madison have been reliably keeping records of the ice-on and ice-off dates since 1855 and that 165 year old dataset reveals some big changes in winter ice cover. As we’ve covered before in this blog, one of the many impacts of climate change on our lakes is that we will eventually line through years where we simply don’t get “ice on” at all. Luckily for anyone who loves ice fishing or skating or simply walking the frozen shoreline of a lake, we’re not there yet. But our lakes are, on average, freezing later and thawing sooner and, as you can see in the graph below, we’re trending towards less and less ice.

Another issue that our shift in winter freezes and spring thaws has highlighted is the importance of lake ice safety. Recent research from a team of limnologists, including Center for Limnology director emeritus (and avid lover of lake ice) John Magnuson, shows that winter drownings are up around the globe, especially for young adults and children, in places where lake ice seasons are shrinking – a result likely tied to the fact that lake ice is especially dangerous during a lake’s transition between frozen and thawed.

But don’t think that we’re advising folks to turn their backs on our amazing frozen resources. Here in Madison, like many, many places on earth, the winter freeze is a big part of our culture and recreation. We realize that people will venture out on our lakes this winter. And, while there is no 100% method for ensuring that ice is safe, these guidelines from the Wisconsin DNR can help make sure you’re minimizing risks as you enjoy one big perk of winter while we’ve still got it!

A stroll along the frozen nearshore waters of Lake Monona. Photo: A. Hinterthuer