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Send us your Ice-IN dates!

We are collecting data about when lakes freeze over in the late fall/winter. You may have heard about collecting ice-out data in the spring, which sets the clock ticking for lake layers to set up for the summer months (once the lake layers are established, they generally do not mix and the oxygen levels at the bottom of the lake will decrease over time). Increasingly, scientists are tracking ice-in as well, to understand how the length of time under the ice affects lake health.

We typically think of ice-out in the spring as a time when waters are first navigable — meaning 80% or more of the ice is gone. Ice-in can be more difficult to discern, and lakes can freeze and thaw multiple times before a final freeze for the winter. Let’s think of it as completely or nearly completely covered in ice. We will collect data of the first instance of ice-in as well as when the lake is covered over for the winter. Please note that skim ice is not ice-in, so check back the following day as the temperature decreases. Wind, sun, precipitation, and of course, temperature will all contribute to (or delay!) ice-in.

Water is a miraculous molecule, which we regularly share with (and attempt to inspire) our students in school. Its properties allow the solid form to be less dense than the liquid form (hence ice on the surface of the pond, and floating ice in our tea). Water is most dense at 4 degrees Celsius (about 39 degrees Fahrenheit). Ice cover allows animals to take refuge under the blanket of ice, protected from the desiccating and freezing temperatures of winter.

So, take a peek out the window of your lakefront space and watch the ice freeze over the water, and let us know! If you’re not in Maine, please consider reaching out to a neighbor to share this important information with us. When you have ice-in dates, please send to along with your name, name of water body, town, and county the water body is in, ice-in date, any previous ice-in dates and thaws, and any other cool observations you’d like to share. Thanks so much for helping to advance lake science!

We share data with the Lake Stewards of Maine and the Department of Environmental Protection as we collectively look towards better understanding lakes in winter.

Check out this short video of clear ice-in on the Boundary Waters in Minnesota early December. This happened a few years ago on Highland and you might have seen the LEA crew out ice skating!

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