Spatiotemporal Hydroclimatic Heterogeneity Across Odisha, India (1981–2025): Changing Rainfall–Temperature Regimes, Drought and Climate Extremes

Abstract Changes in rainfall and temperatures are basic elements of a regional climate system, but they are not often spatially uniform over time. This is relevant in monsoon-dependent regions where atmospheric moisture and thermal conditions affect agriculture and water resources, as well as exposure to climatic extremes. In this study, the hydroclimatic variability has been assessed at the district level over a 45-year period (1981–2025) for observations from the India Meteorological Department (IMD) that are gridded on a daily basis. The analysis considers three 15-year periods: 1981–1995, 1996–2010, and 2011–2025, across all 30 districts. Standard deviation and the coefficient of variance were used to assess the patterns and variability of annual rainfall, annual maximum temperature (Tmax) and annual minimum temperature (Tmin). The trend direction was evaluated with the Mann–Kendall test, and the magnitude of the trend was estimated by Theil-Sen's slope. The annual rainfall (mean) is consistent in the west–east gradation, about 1200–1300 mm per year in the interior and almost 1700 mm per year at the north-eastern coastal district. The number of districts with positive annual rainfall trends decreased from seven in 1981–1995 to one in 2011–2025. Tmax depicts an intensifying warm core over north-central and western interior districts (Sundargarh, Jharsuguda and Sambalpur), with an overall spatial warm pattern persisting. The 1-month SPI shows a drying trend, particularly during 1996–2010, which was somewhat moderated during 2011–2025. Tmax shows an intensifying warm core over north-central and western interior districts, particularly Sundargarh, Jharsuguda, and Sambalpur. Hythergraph analysis indicates persistent hot–dry pre-monsoon conditions and increasing thermal stress in interior districts, together with shifts in monsoon rainfall concentration. These findings indicate significant hydroclimatic variability in the State of Odisha and the need for district-wise climate risk mapping and adaptation planning, especially in rain-fed agricultural areas. The study also offers a unified approach to investigating changing rainfall–temperature regimes in monsoon-dependent regions.