This season’s ice-in date was Dec. 13, 2024, making for a total of 123 days of ice cover — inclusive of the ice-in date and exclusive of the ice-out date. The figure is right around average for the last 20 years, although below the overall historical average, which goes back to 1903, according to Phil Snyder, the Ausable Freshwater Center’s water quality research manager.

“That is actually right on average for the 20-year record,” he said. “The ice cover has diminished over the period of the record, and that’s largely due to a later ice-in. … (This season) is still significantly shorter than it would have been 125 years ago.”

The Mirror Lake ice in and ice out dates for the previous six years are as follows:

– 2024: Ice in – Dec. 13; ice out – April 1; duration – 101 days

– 2023: Ice in – Dec. 22; ice out – April 14; duration – 122 days

– 2022: Ice in – Dec. 13; ice out – April 14; duration – 115 days

– 2021: Ice in – Dec. 20; ice out – April 9; duration – 114 days. (Ice first formed on the lake on Dec. 9, melted on Dec. 12 and then froze over on Dec. 20.)

– 2020: Ice in – Dec. 16; ice out – April 6; duration – 127 days. (Ice first formed on the lake on Dec. 11, melted later that day and the next, then froze over on Dec. 16.)

– 2019: Ice in – Dec. 1; ice out- April 22; duration – 150 days

The Ausable Freshwater Center defines ice out as Mirror Lake being navigable from one side to the other, meaning that days where the lake is partially frozen over — such as Monday, April 14 — count toward the ice cover.

Snyder said it was important to have such a long-running ice cover observation record as Mirror Lake provides. While the data is not completely continuous — there are 11 seasons without duration records — the overall span is one of the longest in the state.

“It’s valuable for a couple of reasons,” he said. “You have the long-term climate record so you can track the larger changes that are occurring over that period of time — more data is always better than less. On the shorter end of things, ice cover affects the way a lake behaves.”

A longer period of open water means the lake gets more sunlight. Snyder said this generally results in more vegetative productivity and warmer temperatures, which affect the lake’s stratification and subsequently, the size of the layer that cold-water species, such as lake trout, can live in, with warmer lake conditions cutting down on the amount of habitat.

“Your max temperature might not necessarily be higher, but you’re going to have higher temperatures for a longer duration,” he said.

The Ausable Freshwater Center works in conjunction with the Paul Smith’s College Adirondack Watershed Institute to monitor Mirror Lake water quality year-round, with support from the North Elba Local Enhancement and Advancement Fund grant program, the Mirror Lake Watershed Association, town of North Elba, village of Lake Placid, Ironman Foundation, the state Department of State and private donors.