This study investigates the temporal and seasonal trends of key climatic parameters within the Doon Valley, including maximum temperature (°C), minimum temperature (°C), precipitation (mm), and relative humidity (%). Utilizing data from the National Aeronautics and Space Administration (NASA) Prediction of Worldwide Energy Resources (POWER) Modern Era Retrospective-analysis for Research and Applications (MERRA-2), we analysed daily, monthly, and annual datasets spanning from 1981 to 2023 using R software version 4.4.1. The analysis covers four distinct seasons: Pre-Monsoon (March to May), Monsoon (June to September), Post-Monsoon (October to November), and Winter (December to February). Significant temporal variations (P < 0.05) were detected for all assessed parameters. Notably, maximum temperatures during the Monsoon season, particularly in June, exhibited a significant decline of -1.99°C (6.30%) from 1981 to 2023. In contrast, minimum temperatures increased significantly during the Post-Monsoon season, rising by 2.85°C (24.57%). Precipitation rates and occurrences saw a substantial increase during the Monsoon season, with a notable rise of 384.48 mm (42.65%) in July and August. Additionally, relative humidity showed a significant increase across all seasons, rising by 24.50%. These findings highlight the major climatic alterations in the Doon Valley during the last four decades. These findings provide insights into changes in temperature and precipitation trends, which could affect water resources and aggravate environmental hazards. This underscores the need for effective water resource management and climate adaptation strategies to mitigate these effects on the ecosystem and local communities.