The aim of the paper was to develop a model determining production effects of corn irrigation depending on a drought level in the growing season.Corn is particularly useful for cultivation in the conditions of irrigation since its yield in central Poland depends significantly on rainfall distribution in growing season. Corn was grown under irrigation conditions in the years 2005-2016 in the region of central Poland, meteorological data, were gained from the research station of the UTP University of Science and Technology in Bydgoszcz. Based on the results of twelve-year effects of corn irrigation and meteorological data, the most relevant relationships between irrigation productivity and chosen indices during the period of high water needs of corn (from 1 June to 31 July) were searched. The following indicators were taken into account: absolute precipitation totals, relative precipitation index (RPI), standardized precipitation index (SPI) and the ratio of precipitation to reference evapotranspiration. The results shown that yield of non-irrigated corn were characterized by a very high variability and depended significantly on indicators, based mainly on rainfall conditions. The production effects of drip irrigation correlated significantly with the indicators during the period of high water needs of plants, covering June and July. In wet periods the increases in grain yields due to irrigation were non-significant and about four-fold lower and in the dry seasons -more than half higher than the average increases. There is a high importance of the results presented in the paper, because they can be used as a model for forecasting corn production and its economic effects as well as for planning the development of irrigation systems in a given area.