This study investigates the spatiotemporal characteristics and drivers of drought across Iran from 1991 to 2020 using the Standardized Precipitation Evapotranspiration Index (SPEI) and extreme climate indices. The analysis reveals significant variability in drought frequency, duration, severity, and intensity across different climate zones, with the most severe and prolonged droughts observed in Iran’s western, northwestern, and northern regions. The period between 1999 and 2002 marked the most widespread and intense drought, while minor wet spells occurred sporadically in subsequent years. Trends indicate a general intensification of drought conditions, with 87% of the country experiencing a significant negative trend in SPEI, particularly in the west. Moderate drought events predominate, but regions with lower drought frequency experience higher severity and intensity. Temperature and precipitation extremes are key drought drivers: increasing trends in maximum and minimum temperature indices and declining precipitation trends are strongly correlated with heightened drought characteristics, especially in the west and southwest. Further, land use analysis from 1992 to 2020 demonstrates pronounced conversion of wetlands and vegetated areas into barren land and rainfed croplands in regions of extreme and severe drought, while areas with moderate drought witness vegetation degradation and urban expansion. These transformations underscore the compounded impacts of drought, rising temperatures, and land use changes on Iran’s ecohydrological systems, emphasizing the urgent need for adaptive management and further multi-variable analysis to inform sustainable resource planning.

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