Cold overnight temperatures help Lake Mendota freeze, briefly
Ice on! Cold nighttime temperatures, combined with cold water and light winds, helped Lake Mendota officially freeze on December 25, 2024, as declared by the Wisconsin State Climatology Office. Two days later, on December 27th, Lake Mendota reopened as high temperatures climbed well into the 40s. The largest lake in the Yahara Watershed froze for the first time in the 2024-2025 winter season just five days after December 20th, which is the median ice-on date for Lake Mendota. The latest date ice-on has been declared is January 30th, and that took place in 1932.
“We [scientists from the Wisconsin State Climatology Office] were in communication on Christmas Eve and again on Christmas Day, after making our separate visual observations of Lake Mendota,” said Ed Hopkins, Assistant Wisconsin State Climatologist. “We agreed that a thin sheet of ice formed to cover Lake Mendota mid-morning on Christmas… Dense fog prevented us from making any observations on the 26th as the visibility was down to roughly 500 feet… But, the ice was essentially gone on the 27th.”
The Wisconsin State Climatology Office requires ice to hold for a period of 24 hours before a lake can officially be declared frozen over. The December 25th freeze date is three weeks earlier than last winter’s January 15th freeze date. For statistics about determining the freeze date and the Madison ice record, see History of freezing and thawing of Lake Mendota and Madison lakes ice summary.
We have a winner!
For the 14th year in a row, Clean Lakes Alliance held its annual Mendota Freeze Contest. The contest asks people to make a guess as to when the lake will officially freeze. Of the more than 1,300 people to enter the contest, 21 people guessed Lake Mendota would freeze on December 25th. Dan Standiford of Madison is our randomly-selected winner from the 21 people who guessed December 25th. When Standiford was told he won the contest, he said, “I’ve been doing this for a long time and never even come close.” Standiford will receive $1,000 in gift cards courtesy of Lands’ End as the grand prize.
Stay safe!
With the recent mild temperatures, any remaining ice on our local lakes may be quite thin. Ice conditions can change rapidly with weather fluctuations. The Wisconsin DNR recommends waiting for at least four inches of ice to develop before walking on our lakes. If you are venturing out on a lake, always let someone know where you are going or take a friend with you!
Race (or walk) on a frozen lake
Registration for Clean Lakes Alliance’s popular Frozen Assets 5K Run/Walk is open. Participants can choose between a timed 5K race or an untimed 5K walk. All participants receive a t-shirt and kids 10 and under can participate for free with a registered adult. Starting and finishing at The Edgewater, the Frozen Assets 5K is the only race in North America held entirely on frozen lake! Registrations for this event raise important funds for lake improvement projects, water quality monitoring, and education!
Learn about ice cover on Lake Mendota and other local lakes.
