Wisconsin State Climatology Office

DETERMINING THE ICE COVER ON MADISON LAKES

The State Climatology Office maintains a list of dates for the ice over and ice out of three of the Madison area lakes (Mendota, Monona, Wingra).  These records, extending back into the mid-19th century, are based upon the observations made by various people, including those at Washburn Observatory on the University of Wisconsin campus.  Over the last thirty years, our office has made the observations that currently extend the records appearing on this website. We have made every effort to follow the observational practices that would have been used during the 19th century to maintain as consistent and homogenous time series as possible.

The rules of opening and closing determination have been handed down by oral tradition, so there is some question how scientific the dates have been arrived at over the years.  Our vantage point on the 13th floor of the Atmospheric and Spaces Sciences Building on campus (1225 W. Dayton St.) does provide a fair view of the three lakes.  However, closer inspection of the lakes from various vantage points is made.

Lake Monona (as well as Lake Wingra) has a general "50% covered" rule, but often a mere half-iced lake does not look convincingly closed (or open, as the case in the spring), so a bit of admitted subjectivity is involved.  Thus the vantage point of the foot of South Few Street is the prime central location on Lake Monona for asking "does this lake look ice-covered or open?" but consideration from other points is taken as well, such as from the causeway, Monona Terrace, and the northeastern end.  Lake Wingra is most often observed from Vilas Park and sometimes from within the Arboretum. In addition, the date is not fixed until the lake has remained closed at least a full day, so until the ice cover persists into a second day, neither a date of closure nor the beginning of ice cover duration is called.

Determining the opening and closing dates for Lake Mendota is more of a challenge because the length and shape of the lake would require a sufficiently high vantage point that was not readily available to 19th century observers.  Partly because Lake Mendota has a more irregular shoreline, an important secondary criterion applies for that lake:  whether one can row a boat between Picnic Point and Maple Bluff.  This rule arose from the era of E. A. Birge and Chancey Juday (according to Reid Bryson, founder of the UW Meteorology Dept., now known as the Dept. of Atmospheric and Oceanic Sciences), because they frequently were out on the lake in a rowboat, and the ice along that line determined if they could transport a case of beer over to their friends in Maple Bluff.

As a matter of historical interest, a pamphlet was produced in 1935 by Eric R. Miller, the popular head of the Madison office of the US Weather Bureau (1908-1944) containing the listing of the dates for the opening and closing of Lakes Mendota and Monona from 1851 to 1935. The copy of this pamphlet was from the collection of Aldo Leopold (1887-1948), the noted wildlife ecologist at the University of Wisconsin-Madison.

Lyle Anderson
Manager, Wisconsin State Climatology office
1225 W. Dayton St., Rm. 1353
Madison, WI  53706

phone (608) 263-2374

Return to: [Madison Lakes Page] [Madison Climate Page] [State Climatology Homepage]

Latest revision: 9 March 2017

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URL Address: https://www.aos.wisc.edu/oldsco/lakes/msn-lakes_instruc.html