Lake Mendota's 2024 freeze date was the third-latest in its recorded history

Claire Reid, Milwaukee Journal Sentinel
·4 min read

Just a few weeks ago, state climatologist Steve Vavrus said he worried that the lack of ice on Madison's Lake Mendota could damper the capital city's Clean Lakes Alliance's Frozen Assets fundraising event in early February.

Thanks to one of the warmest Decembers in Wisconsin history, as of Jan. 3, Mendota was free of ice. This was out of the ordinary, as the average freeze date for the lake is Dec. 20, according to records kept since 1852.

Since 2012, Frozen Assets has raised over $1.2 million for lake improvement projects, educational programs and water quality monitoring, according to the Clean Lakes Alliance. One of its biggest events is the Frozen Assets 5K, where participants run or walk entirely on Lake Mendota.

Obviously, this can't happen without a frozen lake.

Lake Mendota in Madison shown frozen over this week. Jan. 15, 2024, was the lake's third-latest freeze date since records began being kept over 170 years ago.
Lake Mendota in Madison shown frozen over this week. Jan. 15, 2024, was the lake's third-latest freeze date since records began being kept over 170 years ago.

Thankfully (for the Clean Lakes Alliance at least), the tides have turned dramatically temperature-wise since the beginning of the month. Last week brought statewide snowstorms, while this week has seen multiple days of sub-zero temperatures. The frigid temps were enough to finally freeze Mendota, along with Madison's other major lakes.

On Monday, the Wisconsin State Climatology Office declared that Mendota was officially frozen, with help from the sub-zero temperatures, cold water and low wind. The Jan 15. freeze date was the lake's third-latest freeze date since monitoring began over 170 years ago. Mendota froze three weeks later than last year, when it was declared frozen on Christmas Day.

The state climatology office requires ice to "hold" for 24 hours before a lake can be officially declared frozen. Mendota's latest freeze date on record was Jan. 30, in 1932. The only other time the lake froze later than this year was Jan. 20, 2007.

"We feel that the climate has changed here, and the seasons are altering," said Clean Lakes Alliance marketing and communications director Adam Sodersten. "(The freeze date) is being pushed further forward, and the freeze duration is shortening. The duration used to be a little over 100 days, and, at this rate, we'd be lucky to get 80-to-90 days."

Lake Mendota in Madison shown frozen over this week.
Lake Mendota in Madison shown frozen over this week.

When is the 2024 Frozen Assets 5K?

Although temps are very low right now, rain and temperatures in the upper 30s are in forecast for Madison next week. So, the Clean Lakes Alliance is still worried that the 5K may have to be canceled, though less worried than they were two weeks ago, Sodersten said.

"We look for roughly eight inches of ice at a minimum to hold stuff on the lake," he said. "So, what we need to do is, we need good ice to build between now and the Feb. 3 event."

Sodersten said the organization's plan is to begin drilling test holes in the ice next Wednesday to see if it's fit to hold the 5K and other Frozen Assets events.

If not, the fundraiser will still go on with on-land events only, including ice science demonstrations, a figure skating show and skating on the Edgewater Hotel ice rink.

Frosted trees catch the sunrise, reflecting off snowy, frozen Lake Wingra in Madison, Wis., in February 2020.
Frosted trees catch the sunrise, reflecting off snowy, frozen Lake Wingra in Madison, Wis., in February 2020.

When did Madison's other lakes freeze this winter?

With Mendota finally frozen, all of the Madison area's major lakes in the Yahara River Watershed are now iced over, the Clean Lakes Alliance shared. As the watershed's largest lake, it is typical for Mendota to freeze last.

Here's when the other lakes froze this year:

  • Lake Wingra: Jan. 5 (It also froze on Dec. 13 and Dec. 19, but thawed on Dec. 17 and Dec. 24).

  • Lake Kegonsa: Jan. 14

  • Lake Waubesa: Jan. 14

  • Lake Monona: Jan. 15

The sun rises above ice formations off the shore of Lake Michigan at Big Bay Park in Whitefish Bay Saturday, Feb. 20, 2021. Due to below-zero temperatures, much of the shoreline is frozen over leaving tree branches covered in ice.
The sun rises above ice formations off the shore of Lake Michigan at Big Bay Park in Whitefish Bay Saturday, Feb. 20, 2021. Due to below-zero temperatures, much of the shoreline is frozen over leaving tree branches covered in ice.

Frozen lake ice safety tips

Even if a frozen lake looks solid, the ice still might be thin, the Clean Lakes Alliance warns. The Wisconsin Department of Natural Resources recommends waiting for at least four inches of ice before walking out on a frozen lake but says no amount of ice is ever "100% safe."

Additionally, large temperature fluctuations, like we'll experience next week, can cause ice conditions to change rapidly.

"If people venture out on the lake on their own, things to remember ― make sure you tell somebody you're going on the lake, bring your cellphone, have a plan as to what would happen if you did go through. ...," Sodersten said. "Avoid open water. Avoid places where water sources are coming in, like a river or an outfall."

For more ice safety tips and how to rescue yourself should you fall through the ice, visit dnr.wisconsin.gov/Education/OutdoorSkills/IceSafety.

This article originally appeared on Milwaukee Journal Sentinel: Lake Mendota 2024 freeze date is third-latest ever recorded