Most agree a lake or pond needs to have at least a 4 inch layer of ice on top for it to be safe to play on. You can use the freezing degree day calculations as outlined below to estimate when that would happen. The amount of sunshine or wind on the lake or pond, the depth of the lake or pond, the overall size and the source of the water all can impact how fast its ice thickens. In New Providence we require 4 inches of ice, which is measured by our Department of Public Works, before skating is permitted .
Some will argue that they can walk on the ice without an issue, so why do they have to wait? Because once the pond is open to skating, there could be dozens of people on the ice. Strong enough to hold a couple of people does not necessarily mean it could hold 50-100 people. The pond in the center is about 5 feet deep – so safety is critical. Additionally, if the ice is broken and refreezes, it could create a safety hazard in the middle of the ice surface.
How long does it take for 4 inches of Ice to form?
When cold air is in place, the top layer of water will begin to cool as it comes into contact with the cold air. If the cold air is around long enough, that top layer of lake water will drop in temperature until it freezes. Ice is less dense than water, so the ice will float on top of the water. If the cold air stays in place, the ice will grow thicker and thicker. However, that top layer of ice insulates the heat from the bottom of the pond, so it is not a fast process.
Scientists have developed a formula for calculating how fast ice will freeze on a lake. Here’s how:
1. Calculate the average temperature of the day by adding low temperature and high temperature and dividing by 2. Use degrees Fahrenheit. Now subtract that average from 32 degrees, the temperature at which water freezes. You have now just calculated what they call “freezing degree days.” Example: If the low temperature today was 24 degrees and the high was 30 degrees, the average temperature of the day was 27 degrees. Subtract that from 32, and you get 5 freezing degree days for this day.
2. Based on studies, once a thin layer of ice film forms on a lake, it will add 1 inch of ice for every 15 freezing degree days in a 24 hour period. Example: If we had a day with 5 freezing degree days, you would use the formula 5/15 = .33. On this day you would add .33 inches of ice, or 1/3 of an inch. But remember, this is after the first layer of ice forms.
Therefore, even if the temperature drops dramatically for a day or two, it is unlikely that sufficient ice will form.
Signs will be posted at the pond indicating whether skating is permitted. Please obey the signs and set a good example for your children. Once the pond is open for skating, the borough website will be updated.
We appreciate your cooperation and understanding.