The National Weather Service's North Central River Forecast Center has a map available online which shows frost depths. The map shows various soil temperatures, as well as frost depths that range from 2 to 60 inches.
Frost depth, which is also known as freezing depth, refers to the depth at which the soil's water is supposed to freeze. A map that shows frost depth when it is calculated under vegetation or bare ground can be useful for activities such as grave digging, construction and agriculture. Hydrologists may also find these maps beneficial for their water runoff calculations.