Drought has become a recurrent phenomenon in Turkey in the last few decades. Significant drought conditions were observed during years of late 1980s and the trend continued in the late 1990s. The country's agricultural sector and water resources have been under severe constraints from the recurrent droughts. In this study, spatial and temporal dimensions of meteorological droughts in Turkey have been investigated from vulnerability concept. The Standardized Precipitation Index (SPI) method was used to detail geographical variations in the drought vulnerability based on frequency and severity of drought events at multiple time steps. Critical (threshold) rainfall values were derived for each station at multiple-time steps in varying drought categories to determine least amount of rainfall required to avoid from drought initiation. The study found that drought vulnerability portrays a very diverse but consistent picture with varying time steps. At regional scale, south-eastern and eastern Anatolia are characterized with moderate droughts at shorter time steps, while the occurrence of severe droughts at shorter time steps is observed at non-coastal parts of the country. A similar picture was observed with very severe droughts. The critical (threshold) values exhibited rising numbers during the growing season at 3-month step in the South-eastern Anatolia, which might have significant consequences considering presence of large irrigation projects underdevelopment in the region. In general, rainfall amounts required for non-drought conditions decrease from the coastal parts toward the interiors with increasing time steps.

Delineation of homogenous precipitation regions can be rather challenging when considerable spatial variability and seasonality of precipitation exist within a large geographic domain. This study aims to investigate and redefine the spatio-temporal variability of precipitation clusters of Turkey by K-means clustering at different time scales. The monthly precipitation of 234 stations for the 1980–2020 period was included. Five precipitation clusters are identified for the 1980–2020 period, while the clusters varied between four and eight and four and six for the 5-year and 10-year sub-periods, respectively. The clustering structures exhibited indicated certain links to the prominent teleconnection patterns. The monthly precipitation correlated more significantly with Arctic Oscillation (AO) in the Aegean and Mediterranean regions, while North Atlantic Oscillation correlated better with the Eastern and Southeastern Anatolian stations. The variability of the cluster structures is described in association with the coefficient of variation (COV) spatial patterns using the observed station data. At 5-year and 10-year subsequent periods, no significant variability in the cluster patterns was observed in the lower COV areas where the monthly precipitation was more uniform throughout the year, while more inter-decadal variability was prominent in the higher COV areas where seasonality in precipitation was more pronounced. Overall, the precipitation regions were not spatially coherent over time, and considerable variability was revealed between different regions of the country.