Ice Thickness Safety

It is important to remember that big lakes and ponds don’t freeze at the same time and don’t always have the same ice thickness throughout the entire body of water. More often than not, the center of the body of water has the thinnest ice. What this means for you? Well if you don’t have to drive on the ice, don’t do it. Since most bodies of water freeze in different ways, this could turn a normal winter day into a bad day real quick. When ice fishing and ice skating, stay closer to the edge of the body of water.

If you want to calculate how long it will take for a lake to freeze, you’ll have to measure the high and low temperatures and do some simple calculations.

1. Calculate the average temperature for the day. You can do this by adding the high and low temperature (in Fahrenheit) of the day and dividing it by 2. Now subtract the average from 32 degrees (the temperature at which water freezes) and you will have calculated the “freezing degree days.”
   
   For example:
   High temperature of the day = 30 degrees F
   Low Temperature of the day = 24 degrees F
   30 + 24 = 54
   54 / 2 = 27
   32 – 27 = 5
   5 freezing degree days
    
2. Now based on a lot of different studies, once a thin layer of ice forms on the lake, it will add one more inch of ice for every 15 freezing degree days in a 24 hour period
   
   Now assume there already if a thin layer of ice on the lake. For the example above with 5 freezing degree days, you would use the formula:
   5 / 15 = .33
   So on the day used in the example above, you would have .33 of an inch (1/3 of an inch) of ice growth.

"Formulas such as this are empirical, meaning they are calculated only with observed data, so they really are simplifications of the ice growth processes. The formulas assume that the ice growth occurs in calm water and is reasonably consistent, and they do not take into account sea ice motion, snow cover, and other surface conditions." (National Snow and Ice Data Center)