Data used in this work concerning the yielding of 9 medium-early cultivars of potato and sums of precipitation (in the years 2010-2013) were obtained from six COBORU (Research Centre for Cultivar Testing) stations: Karżniczka, Naroczyce, Słupia, Sulejów, Uhnin and Węgrzce. The analysis of precipitation impact on potato yielding in particular months was based on polynomial regression calculated using the GRM module in STATISTICA 10.0. The highest average potato yield was obtained in Naroczyce, while the lowest in Uhnin. In most of the stations the yielding of medium-early cultivars of potato depended in a parabolic way on precipitation sums in particular months of the growing season. April precipitation determined the yielding of cultivars grown in Uhnin, while May precipitation – in Karżniczka, Słupia and Sulejów. In May there was also noted a negative linear impact on tuber yields of potato grown in Węgrzce. Regardless of the location, May precipitations, determining the highest yields, were at the level from 60 to 80 mm. June precipitation within the range of 120 mm determined the obtainment of the highest yields of tuber in Słupia and Sulejów. In the second period of the growing season, July precipitation above 80 mm had a negative impact on the yielding of medium-early cultivars of potato in Karżniczka. In Słupia and Sulejów the maximum yields were obtained when the precipitation ranged from 110 to 120 mm. August precipitation at the level of 70 mm determined the highest yields in Naroczyce and Węgrzce. Data used in this work concerning the yielding of 9 medium-early cultivars of potato and sums of precipitation (in the years 2010-2013) were obtained from six COBORU (Research Centre for Cultivar Testing) stations: Karżniczka, Naroczyce, Słupia, Sulejów, Uhnin and Węgrzce. The analysis of precipitation impact on potato yielding in particular months was based on polynomial regression calculated using the GRM module in STATISTICA 10.0. The highest average potato yield was obtained in Naroczyce, while the lowest in Uhnin. In most of the stations the yielding of medium-early cultivars of potato depended in a parabolic way on precipitation sums in particular months of the growing season. April precipitation determined the yielding of cultivars grown in Uhnin, while May precipitation – in Karżniczka, Słupia and Sulejów. In May there was also noted a negative linear impact on tuber yields of potato grown in Węgrzce. Regardless of the location, May precipitations, determining the highest yields, were at the level from 60 to 80 mm. June precipitation within the range of 120 mm determined the obtainment of the highest yields of tuber in Słupia and Sulejów. In the second period of the growing season, July precipitation above 80 mm had a negative impact on the yielding of medium-early cultivars of potato in Karżniczka. In Słupia and Sulejów the maximum yields were obtained when the precipitation ranged from 110 to 120 mm. August precipitation at the level of 70 mm determined the highest yields in Naroczyce and Węgrzce.