More precisely, the temperature underground is very stable. At 8-12 feet there is little to no variation over the course of a year. So in a cold season it will

More precisely, the temperature underground is very stable. At 8-12 feet there is little to no variation over the course of a year. So in a cold season it will be warmer underground than ambient (this is why foundations are dug “below the frost line”) while the opposite is true during a warm season.