Surveys of ground frost in three peatland types, sedge fen, transitional (tamarack) fen, and black spruce – Sphagnum bog, in central Saskatchewan showed differences in depth of freezing and rates of thawing. The maximum depth of freezing and most rapid removal of ground frost occurred in the fen and transitional fen. Seasonal frost was found in the bog until late August. Thawing occurs primarily from the surface downward. However, some thawing from below may occur in the fen. Thawing from the surface is strongly related to the number of thawing degree–days.