The 2021 ice-out date for Detroit Lake was on Sunday, April 4, about two weeks earlier than average over the previous 30 years, according to Dick Hecock, a former geography professor who tracks lake ice statistics.
Though Little Detroit was substantially ice free a couple of days before, as usual, a large mass of ice remained on Big Detroit, he said in an email.
On Sunday at mid-afternoon, a mass of residual floating ice was still clinging along the East Shore of Big Detroit, but the lake was more than 95% ice-free, in accordance with Minnesota DNR guidelines for ice-off determination, Hecock reported.
The April 4 date is about two weeks earlier than the average of the previous 30 years. It is noteworthy that there is no trend in ice-out dates over this period.
April 4 is the fifth earliest date in the last 30 years, with earlier dates in 2012 (March 23), 2016 (March 29), 2010 (April 2), and 2000 (April 3). Twice in that period (May 5, 1996 and May 12, 2013) ice-outs came more than a month later.
This year, the lake was covered with ice for 139 days, about five days shorter than the 30-year average.
The longest ice-cover duration was 1996 with 177 days, and the shortest was 2000 with 110. There is no discernable trend in duration of ice-cover for this period, either, though the average for the entire 111 year record is about 10 days longer than recent decades.
Hecock began reporting ice-in and ice-out data in 1993 to Ralph Anderson at Detroit Lakes Newspapers in 1993. Anderson provided Hecock with the earlier dates, some of which extend back to 1893. The Detroit ice record is one of the longest for Minnesota lakes, and has been used in several studies of lake ice trends, Hecock said.
The current reports also are forwarded to the State's Department of Natural Resources, the Pollution Control Agency and the State Climatological Office.