Frost in the ground

I just did 2 probe checks for frost. The first check in the lawn showed only minor frost, maybe an inch deep. In the tilled garden where most of the soil is bare, frost was about 4 inches thick. I was expecting another layer deeper, but that deeper frost must be thawed. The good thing about thin frost is that water can percolate through the soil and move deeper. This will shorten the saturation time when the weather warms and dries out.