Trends and variability of rainfall and related extreme indices with implications for climate sensitive planning in Kirehe district of the eastern province of Rwanda

Rainfall variability and extremes critically influence ecosystems, agriculture, and livelihoods, particularly in climate-sensitive regions such as eastern Rwanda. This study investigates spatial and temporal patterns of rainfall and related extreme indices in Kirehe District using daily observational data from the Rwanda Meteorology Agency covering 1983–2021. Key rainfall characteristics-onset and cessation dates, seasonal length, and number of rainy days-were derived using rainfall-dry spell and evapotranspiration criteria. Extreme rainfall indices were computed following the Expert Team on Climate Change Detection and Indices (ETCCDI) methodology, while variability and trends were analyzed using the coefficient of variation, modified Mann–Kendall test, and Sen’s slope estimator. Results reveal three near-homogeneous climatic zones across Kirehe District. Region 1 (R1) is characterized by an earlier onset, later cessation, longer growing season, and more rainy days, whereas Regions 2 (R2) and 3 (R3) exhibits later onset and cessation, shorter seasons, and fewer rainy days. Rainfall variability is highest in central and southern areas, particularly for onset dates, seasonal length, and number of rainy days. Extreme rainfall indices show strong spatial contrasts, with consecutive dry days (CDD) and heavy precipitation events (R10mm, R20mm, RX1day, RX5day) varying markedly across the district. Although no significant long-term trends are detected for total rainfall or seasonal parameters, localized increases in CWD, PRCPTOT, and R10mm in the north and declines in rainfall intensity indices in the south indicate growing climatic disparities. These findings highlight substantial intra-district rainfall heterogeneity and increasing exposure to both drought and flood risks. The results underscore the need for integrating localized climate information into district-level planning and adaptation strategies to enhance agricultural resilience and water resource management in Rwanda’s eastern lowlands.