In this study, the Karaisalı region of Turkey, which has a semi-arid climate and is known to contain the extensive plains and rich water resources of the Seyhan Basin, was preferred as a study area for investigating wet and drought periods for a long timescale. Forty-one years of total precipitation data, between 1980 and 2020, belonging to the closest precipitation observation station located in the Karaisalı region were used. By using the Standardized Precipitation Index (SPI), which is one of the frequently used meteorological drought indices, drought classification probabilities, expected first transition period and residence time in each drought severity class values were calculated for the 12-month time scale. As a result of the study, it was determined that the most drought period took place in 2012 according to the examined time duration. In addition, the most wet period was observed in 2001. When various time scales were considered, SPI-3 and SPI-6 have Near Normal Wet periods, while SPI-9 and SPI-12 have Near Normal Drought periods. Extremely Wet periods were more numerous, while Extremely Drought periods lasted longer. In addition, 3 months after the end of the drought categories, it can be seen that the Wet and Drought periods change into Near Normal Wet and Near Normal Drought periods.