This elaboration was based on yields of nine medium-early cultivars of potato grown in Karżniczka station belonging to COBORU(Research Centre for Cultivar Testing) and on monthly precipitation sums during the growing season (April – August). For each of the cultivars separately in subsequent years and for precipitation sums in particular months of the growing season (IV–VII) polynomial regression models of precipitation – cultivar’s yield – were calculated. At the beginning of the growing season the yield of medium-early cultivars of potato was negatively correlated with monthly precipitation sums, while in the final stage of vegetation – this correlation was positive. The lowest yield of Stasia cultivar was noted with monthly precipitation sum of 34–38 mm in April, Tajfun cultivar with May precipitation from 100 to 120 mm, Finezja and Jurek cultivars with monthly June precipitation of 120 mm. Whereas maximum yield of Cekin and Jurek cultivars was noted with August precipitation of about 100 mm.