Lake Monona appears frozen at long last. Though its broad expanses of ice remained dotted with a few areas of open water on yesterday, Lyle Anderson, manager of the Wisconsin State Climatology Office, had tentatively identified Thursday, Jan. 18, as this year's official freeze date for Lake Monona. By this afternoon, that determination had been confirmed, making this the second-latest freeze date on record for Lake Monona. And tonight's forecast low near 5 degrees with light winds ought to yield favorable conditions for closing whatever stubborn puddles remain.
Freeze and thaw dates for both lakes Monona and Mendota have been kept for 150 years. Those records are now maintained by the state climatologist's office. The mark for latest freeze on both lakes is Jan. 30, 1932. Until this year, the second-latest freeze for Lake Monona had been Jan. 14, recorded in 1890 and tied in 2000.
"The rules of opening and closing determination have been handed down by oral tradition," notes Anderson in an email exchange, "so there has been a bit of discussion about how scientific the dates have been over the years. Lake Monona (as well as Lake Wingra) has a general '50% covered' rule."
By that measure, Lake Monona might have been considered closed two or three days ago. Anderson, however, adds that "in recent practice a mere half-iced lake doesn't look convincingly closed." Bottom line: Making the call on a freeze date involves "a bit of admitted subjectivity."
Anderson says he relies on the view from Few Street "as the prime central location for asking, 'Does this lake look ice-covered or open?'" But he also considers observations from Monona Terrace, the John Nolen causeway and other vantage points.
Yahara Place Park provides the vantage point for this video clip, filmed late Friday morning, Jan. 19, 2007. The distant light and dark areas are faint, but indicate water rather than ice.
Anderson adds that while Lake Mendota's ice shelves are expanding along its shoreline, it remains "still very much 'open.'"
And he relates an amusing anecdote -- perhaps apocryphal -- regarding the standards for determining Mendota's freeze date. It involves the pioneering early 20th-century UW limnology professors Edward A. Birge and Chancey Juday, and Anderson ascribes it to emeritus UW environmental studies Prof. Reid Bryson.
"Partly because Lake Mendota has a more irregular shoreline," Anderson writes, "there is an important secondary criterion: whether one can row a boat between Picnic Point and Maple Bluff. This rule arose from the era of Birge and Juday (according to Reid Bryson), 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. Whether there is solid documentation for this or not, it conjures a charming image."
It does indeed.