In recent years extreme hydrological events are becoming more frequent and pronounced. In comparison with flood drought is a much more complex phenomenon because it is difficult to determine its beginning and end; furthermore its occurrence is very difficult to limit in time and space. It also causes considerable economic damage. In general the primary cause of drought is the lack of rainfall, and at the same time also time of the occurrence of the rainfall deficit, its distribution and intensity in a specific area. There are various indicators that determine time and space dimensions of drought. One of the most frequently used is the standardized precipitation index (SPI), the calculation of which requires only data of rainfall for at least a period of 30-years. In the thesis we calculated the values of SPI index for twenty selected meteorological stations in Slovenia for the period 1951 to 2014 on six time scales. We found that on shorter time scales larger number of drought appeared, but since 1990 increased drought periods with greater intensity were observed. Drought does not occur uniformly and simultaneously throughout Slovenia, however it occurs in similar patterns at similar spatial and climatic conditions.