Maine has a long history of keeping records of ice coverage.  For example, Lakes Auburn, Moosehead, Sebago, Damariscotta, Cobbossee, have ice-on and ice-out records dating back to 1850 or earlier. “Ice-on” refers to the date when ice has covered an entire lake, and “ice-out” indicates when the ice has thawed enough to navigate through open water across the entire lake.

Ice Coverage Comparison

Determining ice-on and ice-out dates can be subjective (partial versus full ice coverage, multiple freezes and thaws early and late in the season), but long-term analyses of these records show that lakes across the northern hemisphere have later ice-on and earlier ice-out dates now than they did in previous years.  The change in dates is two weeks on average, which corresponds to our (on average) shorter winters.

After a decently long and cold winter (depending on who you ask or how many Maine winters you have experienced), we’re now awaiting ice-out. While we prepare the boats for the open water season, here’s a look at how this year’s ice coverage measures up to the past. Keep in mind measurements were recorded at the water quality monitoring stations. Ice thickness varies across lakes, some coves had 30+ inches this winter!

Ice thickness

Panel: Ice thickness of lakes in the Belgrade watershed from 2023-2036 (measured at water quality monitoring stations).

Why Tracking Matters

Measuring the thickness and color of ice is the best way to assess ice strength. Black ice is the strongest ice as it contains very few air bubbles and is formed when calm water freezes. White ice is formed when snow and slush partially melt and re-freeze, which traps air bubbles, making white ice less sturdy. There are fewer records of ice thickness on lakes in Maine compared to ice-on and ice-off dates, however, some historic data from the early 1970’s shows that we have much less ice now than we did 50 years ago.

Comparing ice thickness

The graph shows measurements by Davis (1978) of 28 to 30 inches in the 1970’s on Great and Long Ponds compared to 10 to 15 inches in recent years. Looking closer at the last three winters, we can see how variable ice conditions can be. Lake ice measured by 7 Lakes Alliance staff grew to between 15 and 20 inches in 2023, 2025, and 2026, but only 5 to 10 inches in 2024 when we had a very late ice-on date.

Keeping track of ice thickness, ice-on, and ice-out helps us understand how these pastimes could be impacted in the future. We hope you enjoyed the lakes this winter whether you were out fishing, skating, or admiring them from a distance.

If you have questions about data referenced in this article, please contact Lake Scientist Matt Farragher or stop by the 7 Lakes Alliance office.  Happy Mud Season!