Rainfall Dynamics in Sri Lanka Over Five Decades (1970–2023): Implications for Agricultural Adaptation to Climate Change

Climate change is affecting agricultural productivity and economic stability across many parts of the world, but small islands like Sri Lanka are more vulnerable to the effects of climate change. As a result, assessing recent rainfall dynamics is crucial for developing effective climate adaptation measures. This study analysed rainfall data from 44 meteorological stations across Sri Lanka's dry, wet and intermediate climatic zones spanning 54 years (1970–2023) to evaluate rainfall dynamics. The analysis employed multiple statistical methods, including the coefficient of variation (CV), Precipitation Concentration Index (PCI), Standardized Precipitation Index (SPI), Mann–Kendall (MK) test with Sen's slope estimator and innovative trend analysis (ITA). Results revealed increasing annual rainfall trends at 79.5% of stations, with 40% showing statistically significant increases ( p < 0.05), particularly pronounced in the eastern and south‐eastern areas of the dry and intermediate zones. Rainfall variability ranged from 12.9% to 35.4%, with higher variability concentrated in northeastern, eastern and southern regions, while the western wet zone exhibited lower rainfall variability and more consistent precipitation patterns. SPI analysis showed that 70% of years experienced near‐normal conditions, while extreme wet and dry events occurred in 2.67%–4.13% and 2.4%–3.5% of years, respectively. Seasonal analysis demonstrated contrasting trends between monsoon systems: the northeast monsoon‐dominated Maha season showed increasing rainfall at 82%–91% of stations, with 30% exhibiting significant increases ( p < 0.05). In comparison, the Yala season displayed increasing trends at only 56% of stations. Notably, intermediate zone stations (Wellawaya, Nikaweratiya) recorded higher wet year frequencies, while traditionally wet zone areas (Awissawella) experienced increased dry conditions, suggesting potential shifts in the climate zone boundary. These findings provide critical insights into agricultural adaptation to climate change, emphasizing the need for zone‐specific adaptation measures.