Plants of Medicago falcata ’Anik’ were samples to assess their relative cold hardiness during the fall, winter and spring periods from 1974–75 to 1978–79. Precipitation and soil temperature patterns and cold hardiness profiles varied considerably from year to year. Environmental conditions in the fall appeared to exert the greatest influence on the cold hardiness profile and the maximum cold hardiness level in mid-winter. In general, plants started to harden in mid-September, but during one fall hardening period there was a delay associated with the early development of crown buds and the accompanying flush of growth during August and September. During two fall hardening periods, water-saturated soil conditions were associated with a dehardening phase in October. Conditions favoring delayed fall hardening and complete dehardening in the late fall were also associated with a lower level of hardiness in mid-winter. The maximum hardiness level, and the month during which it occurred, fluctuated considerably each year. Plants began dehardening as soil temperatures increased in late winter and early spring during 3 of the 5 yr. In the remaining 2 yr, plants began to deharden prior to an increase in soil temperature.