Freshwater Society Officially Declares Ice Out on Lake Minnetonka

The Freshwater Society, which since the 1960s has called when the ice is out for the season, declared the lake ice-free as of about 1:30 a.m. Thursday, May 2. It was the third time in a nearly complete 158-year record that ice-out has occurred on that date.

This year’s ice-out is 42 days later than last year, when an unusually warm early spring produced open water on March 21. And the ice-out this year is tied for the third-latest recorded ice-out on the lake.

The median date for ice-out on Lake Minnetonka is April 14.

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Ice-out on Lake Minnetonka is a sign of spring that scientists, naturalists and lakeshore residents have been tracking and recording since at least 1855. Freshwater Society founder Dick Gray, who catalogued the early records and has made his own records since 1968, described the standard for determining ice-out in a 2003 column: “when it is possible to travel by small boat from any one shore to any other shore through any passage on the lake.”

Prior to that, Gray wrote, ice-out sometimes was determined by when a car placed on the ice fell through or when a boat could travel from Excelsior to Wayzata. Read that column.

View a year-by-year record of those dates. View a calendar showing the years in which ice-out has occurred on Lake Minnetonka on dates from March through May. Check out a Minnesota Climatology Working Group record of ice-outs on other lakes in the state.

The Hennepin County Sheriff’s Water Patrol uses a different standard: When it is possible to go by boat from the Patrol’s headquarters in Spring Park through the Narrows and around Big Island without having to significantly alter course because of ice.

Using that formula, the sheriff declared the ice out on Lake Minnetonka as of 4 a.m. on Wednesday, May 1.

Ice-out dates for Lake Minnetonka for 23 of the years since 1855 are unknown. Several years ago, Pete Boulay of the Minnesota State Climatology Office found old Smithsonian Weather Observer records that contained ice-out information for two years – 1863 and 1873 – that had long been missing from the official log.

For years, May 8, 1856, was reported as the latest-known ice-out date for the lake. This year, the Minnesota Climatology Working Group raised questions about that date because of old temperature records showing a very warm April that year. In response, the Freshwater Society removed 1856 from its list of known ice-out dates. That leaves May 5, 1857, as the latest recorded ice-out.

This year’s late ice-out resulted from a colder-than-normal late winter and early spring. Average temperatures in December and January were above the 30-year norms for the Twin Cities. But February was a bit colder than normal, and both March and April were significantly colder than normal.