Ice cover on lakes

About 50 percent of the winter ice cover on Madison's Mendota, Monona and Wingra lakes must melt before ice-out can be declared. 

Q: How is ice-out on Madison’s lakes determined?

A: While permanent ice shanties had to be removed from all Wisconsin lakes by March 16, that doesn’t mean — at least in Madison — that the lakes are free of ice.

Ice-off dates for lakes Mendota, Monona and Wingra are determined by visual observations from points throughout the city, according to the Wisconsin Climatology Office.

Observers subjectively look to see if 50 percent of the lake is covered in ice when determining an ice-out date.

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While the group’s office on the 13th floor of UW-Madison’s Atmospheric, Oceanic and Space Sciences building, 1225 W. Dayton St. offers observers an appropriate view of the three lakes, measurements can be taken from other locations.

Lake Monona ice levels can also be observed from areas such as South Few Street, the northeast side of the lake or Monona Terrace.

Ice levels on Lake Wingra can be observed from Vilas Park or the UW-Madison arboretum.

The rules and procedures for determining ice-on and ice-off dates have been passed down orally, according to the office. Records date back to the mid-1800s.

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