NHDES Volunteer Lake Assessment Program (VLAP) began tracking lake ice-in and ice-out dates in 2011 as there was no central repository for this information in New Hampshire. Tracking both ice-in and ice-out allows the determination of total ice cover days which is another important part of tracking physical, chemical and biological changes to lakes over time. With the erratic weather conditions experienced in recent years, the information can also help track climatological shifts and trends.
"Ice-out" is the term typically used to describe when the ice leaves a lake in the spring. Some consider this to be when the ice has melted and broken up enough to navigate a boat from one end of a lake or pond to the other, or when the lake is completely free of ice. Although ice-out definitions may vary slightly from lake to lake, the important thing is consistency and utilizing the same method to determine ice-out for your lake each year. "Ice-in" is the term used to describe when ice covers a lake in the fall. Ice-in can be more difficult to determine but typically is when the lake is completely or nearly completely covered with ice, however a thin skim of ice is not considered ice-in.
In the above plot, ice out dates are presented as points.
The ice cover dataset is provided in the table below.
|Year||Ice In Date||Ice Out Date||Days of Ice Cover|