Climate prediction using global circulation models (GCM) is contemporary and high-resolution climate models that are significant in efficacious decision-making and concerning methods for mitigating and aligning with the environmental shifts brought by climate change. Due to dearth of data and extremely unstable weather of Subarnarekha Basin, prior research failed to determine any clear, consolidated or precise trend. The proposed research examines the historical and prospective angle of the climatic projections for the watershed in context to the CMIP6-SSPs scenario. In light of the models’ validation and detective selection, area-averaged ground observational data were incorporated while comparing with thirteen Coupled Model Intercomparison Project Phase (CMIP6) models. Mann–Kendall trend test (also MK test wherever needed) and innovative trend analysis played a key role in filtering trends of incorporated CMIP6 model apropos of the twenty-first century. The selected models were adopted based on their highest performance and the resultant favoured EC-Earth3-Veg for precipitation, MRI-ESM1-2-LR for maximum temperature and MRI-ESM1-2-HR for minimal temperature aftermath signified best correspondence with the basin observed data. The EC-Earth3-Veg precipitation projection manifests high (statistically significant) increasing trend for the contemporary twenty-first century by 8.83%, 6.82%, 13.91% and 17.76% liable to Shared Socioeconomic Pathway (SSP) scenario. The MRI-ESM1-2-LR mean annual maximum temperature and MRI-ESM1-2-HR mean annual minimum temperature for the near (long)-term period accelerates with a boom of 0.86 (1.42) °C, 0.66 (2.83) °C, 1.15 (3.51) °C, 1.74 (6.80) °C and 2.85 (4.21) °C, 2.11 (6.74) °C, 1.31 (9.40) °C, 0.90 (13.23) °C, respectively, contemplating four SSP scenarios.