Assessing future temperature and precipitation changes locally is essential for water resources planning and climate change adaptation. This study evaluated Phase 6 Coupled Model Intercomparison Project (CMIP6) models and projected temperature and precipitation in the Mashhad Plain. Daily observations from the Mashhad and Golmakan synoptic stations and outputs from seven general circulation models were analyzed for the 1990–2014 reference period. After annual aggregation, the models were assessed using root mean square error (RMSE), mean bias, and Pearson’s correlation coefficient, and the best model was selected based on the lowest error and bias and the highest correlation. Its outputs were downscaled using CMhyd and the delta change factor method under the “Middle of the Road” (SSP2-4.5) and “Fossil-fueled Development” (SSP5-8.5) pathways for 2026–2050, 2051–2075, and 2076–2100. MPI-ESM1-2-HR had the best overall performance. At Mashhad and Golmakan, precipitation correlations were 0.78 and 0.77, RMSE values were 12.46 and 10.34 mm, and mean biases were 9.34 and 8.87 mm, respectively. For temperature, correlations were 0.83 and 0.80, RMSE values were 2.23 and 2.11°C, and mean biases were 1.01 and 1.23°C. In the far future, temperature increased by about 3°C under SSP2-4.5 and by up to 5.6°C in some areas under SSP5-8.5. Annual precipitation also increased by 4.4% and 8.8%, respectively, with the greatest changes in the northern and western plain. These findings indicate intensified warming and altered precipitation patterns, emphasizing stronger adaptation programs and integrated water resources management.