Spring is heating up, and lake ice is beginning to meet its match. We are seeing rings of open water around many lakes.

Ice on lakes in the metro area has been going out three weeks earlier than last year and four days earlier than long-range records. The same applies to most lakes in southern Minnesota. If the trend continues, “ice-out” on central and northern lakes in the state will be two weeks ahead of last year.

Here is how that happens: The main ice sheet of an individual lake weakens and begins to fracture in large sections when winds become strong enough to move it. This is followed by rapid melting of ice crystals on the edges of the floating sections as they come in contact with the warmer water. Wind will sweep the last ice sheets from the lake. As the sheets are pushed ashore, the remaining ice is generally in chunks up to 7 inches thick and honeycomb-shaped. Some people believe that part of the ice sinks when it goes out, but that is false. Ice is lighter than water.

Some loose ice along a shore doesn’t mean the ice is still in, because a boat can easily be pushed through it. I consider ice-out to have occurred when at least 90 percent of the lake is open.

The ice-out date for any of our Upper Midwest lakes is a significant time because it represents the beginning of a whole new season, a season of open water, waves shimmering in the sunlight, and all that comes with it. People are anxious to get out on the water. Soon fishing boats, canoes and sailboats will appear and docks will go in, and we are off and running into summer.

Listed below are a few examples of Minnesota ice-outs last year, and their median dates over the years.

• Budd Lake at Fairmont, April 29, 2018 (median March 29)

• Fountain Lake in Albert Lea, April 27, 2018 (April 8)

• Lake Harriet in Minneapolis, May 2, 2018 (April 7)

• Lake Minnetonka, May 5, 2018 (April 13)

• Lake Mille Lacs, May 11, 2018 (April 25)

• Leech Lake, May 9, 2018 (April 28)

• Lake of the Woods, May 14, 2018 (May 3)

 

Jim Gilbert’s Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.