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Ice cover tour of Madison's lakes with Wisconsin State Climatology Office

“Ice off” declaration from Wisconsin State Climatology Office

The Wisconsin State Climatology Office declared “ice off” for Lake Mendota and Lake Monona on Sunday, March 31, 2019. Lake Wingra’s “ice off” was declared on March 28, 2019. Lake Mendota recorded 86 days of ice during the winter of 2018/19, while Lake Monona had 97 days of ice and Lake Wingra had 111 days of ice cover.

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Lake Mendota Frozen Dec 2018

It’s Official – ICE ON for Lake Mendota!

Ice on date beats median freeze date by five days

Despite warm weather in Madison over the weekend, cool nights, light winds, and cold water helped Lake Mendota officially freeze on Saturday, December 15th. Lake Mendota, the largest lake in the Yahara Watershed, froze eight days after the smallest lake in the watershed, Lake Wingra, which officially froze on December 7th. Lake Monona officially froze on December 11th. The Wisconsin State Climatology Office requires ice to hold for a period of 24 hours before a lake can officially be declared frozen over. After ice took shape this weekend, staff waited to see whether it would hold out through the warm daytime temperatures. The December 15th freeze date is 12 days ahead of last year’s December 27th freeze date, and a surprising five days ahead of the December 20th median freeze date. The latest freeze date for Lake Mendota was January 30th – which happened in the winter of 1932. The Wisconsin State Climatology Office makes the official determination as to whether the lake is frozen. The climatologists use the same guidelines they have used for decades to determine whether the lakes are iced over. This allows for a continuity in data collection. Read more: Determining ice cover on Madison’s lakes.
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