The depth to which water in soil will freeze in the winter is known as the Frost Line. The depth of the Frost Line is important because it influences the construction of buildings and roads; since water expands as it freezes, infrastructure above the Frost Line can be prone to burst pipes, cracked foundations, and similar problems. However, predicting the exact depth to which the soil will freeze is actually incredibly difficult, depending on detailed information about the weather, the soil moisture and temperature, the thermal conductivity of the soil, and other factors. On today’s episode of Weather Break, Dr. Jon Schrage takes a look at some of the reasons why it is so important to know the depth of the Frost Line in your neck of the woods.
I found online this map of estimated average depths of the Frost Line across the continental United States. It looks pretty reasonable to me, but I can’t help but notice that it claims to be from the “Weather Bureau”, which changed its name to the “National Weather Service” decades ago, so maybe this information is obsolete.