How does ice form on Minnesota's lakes?
MINNEAPOLIS — From skating to fishing, Minnesota's frozen lakes offer 10,000 opportunities.
"Lake ice formation starts pretty much when the temperature gets below freezing," said Luigi Romolo, a climatologist with the Minnesota Department of Natural Resources. "The ice will start to form on the shores, the outer edge of the lake, we call that shore ice, and then it will start to go inward."
With consistently cold temperatures and calm conditions, the ice that forms is clear and smooth. But we know that's not often the case for us here in Minnesota.
"The windier it is, the longer it takes for the actual ice cover to form," said Romolo. "Snow plays a big factor in ice formation because it acts as an insulator. So if you get snow on an ice cover, it will prevent the ice below it from getting thicker. It can also weigh down the ice and cause it to crack."
Lake ice's weakest areas are on flowing water, like streams, under bridges and close to shore.
"Ice thickness can vary even in just a few feet," he said.
Gas holes, caused by stream inlets and aquatic vegetation, can also weaken ice. Areas near logs, rocks, bridges and docks can be dicey, too.
"The clearer the ice, the stronger it tends to be," he said.
White ice is caused by snow melting on top of the ice and refreezing. But white ice is only half as strong as clear ice because it's filled with air bubbles. Ice thickness guidelines should be doubled when traveling on white ice.
"My best advice is to always check the thickness of the ice. If you're drilling and you're not all the way through the ice and you're hitting water, that's a good sign that ice is not safe," he said.
The DNR says there needs to be at least 4 inches of clear ice before you can walk on it, but reminds everyone that ice is never 100% safe.