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.

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.

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

phone (608) 263-2374
fax (608) 263-7679

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Latest revision: 30 August 2007

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URL Address: http://www.aos.wisc.edu/~sco/lakes/msn-lakes_instruc.html