Climatology is traditionally connected to different conditions of the atmosphere. However, many occurrences appear from time to time. Those occurrences are defined as extreme. Nowadays it is important to study extreme occurrences for every geographical area. In this paper we have investigated one segment of extreme climatic conditions in Eastern part of Serbia - adverse characteristics of precipitation. Data for Negotin were analyzed, as a representative of the climate in this area. Extreme values of precipitation in one place were taken as dangerous occurrences. We have calculated thresholds above which we consider daily amount of precipitation as dangerous. Thresholds for dangerous lengths of rainy and droughty periods were calculated, too.