Summary:

Two indices: standardized precipitation index (SPI) and relative precipita-tion index (RPI) analyze the same feature, which is either excess or shortage of precipitation. Having known that, the authors compared SPI and RPI with the use of monthly precipitation sums. The choice of this time period was intentional, since in the literature there has been no classification of precipitation conditions for monthly precipitation sums with the use of RPI so far. Therefore, the aim of the study was to determine the relative precipitation index values for monthly precipitation sums based on standardized precipitation index. The described method of transformation from SPI to RPI is innovative and has no equivalent in the literature. Having used the data from Agro- and Hydrometeorology Observatory in Wrocław-Swojec, the authors proposed the method of identification of precipitation conditions for monthly precipitation sums in this region.