Why does the frost line go deeper when the temperature starts getting warmer?
The frost line, also known as the freezing depth, is the depth to which the ground freezes during the winter. More specifically, it is the water within the soil that freezes. The frost line starts near the surface and gets deeper during the course of the winter. Just as it takes a prolonged period of cold air temperatures to begin the freezing process in the ground, there is also a lag time before warmer temperatures at the surface make an impact on the frost line well below ground level. The frost line may penetrate even deeper during this lag time. Due to differences in wintertime temperatures from region to region, the frost line will be deeper in colder climes, while the ground may not freeze at all in warmer locations. The frost line is important, particularly to builders. Building codes require that foundations be dug at least to the depth of the frost line. Failure to do so would compromise the structural integrity of the building as the ground shifts, or heaves, during the free
