Continuous records of the temperature of potatoes stored in clamps were made in 1942–3 (one clamp) and in 1943–4 (three clamps). In the first year, the temperatures at various positions in the clamp coverings were also recorded.

The temperature at the middle of the potato heap showed a drift with time similar to that of mean air temperature. Deviations of mean air temperature from smooth trend, lasting for about a week, had no effect on the temperature of the potatoes; longerperiod deviations were reflected in the temperature of the potatoes after a lag of about a week. The difference in weekly mean temperature between potatoes and external air averaged about 1–5° C. in 1943–4. In 1942–3 it was greater, increasing to over 20° C. in April, because bacterial rotting of the potatoes following blight infection increased the rate of heat production and caused the clamp to collapse at the end of April.