Various factors such as growth of industries and factories and the environment and forests destruction by human caused increase of greenhouse gases in the earth’s atmosphere. In general, the increase of greenhouse gases is leading to changes in the earth’s climates. The most important effect of climate change is its impacts on atmospheric and climatic phenomena such as hurricanes, floods, hail, drought, heat waves and untimely coldness. One of the first resources affected by these climate changes is water resources, as they will change directly with changes in temperature and precipitation. Global warming has significant effects on hydrological cycle and water resources systems, so it could be considered as a major threat for water resources systems all over the world. Climate change studies and consideration of climate scenarios in future period is one of the most efficient methods for analysis of this phenomenon in the future. At present, the most reliable tool for generating climate scenarios are the three-dimensional coupled atmosphere-ocean general circulation models that called AOGCM. This study explores climatic conditions of Mashhad, Gorgan and Oroumieh synoptic weather stations for three near-term, middle and far periods to the year 2100 by using SDSM software and HADCM3 model data under A2 emission scenario. The results of the calibration and validation of temperature and precipitation as climatic parameters in studied stations show the desired accuracy in estimating the parameters in the final output, so the downscaling process can be done for future periods. The results showed that the mean minimum and maximum temperature and annual rainfall will have an incremental trend until 2100 in studied stations. Also the temperature change in Gorgan station is negligible in comparison with two other stations, this shows the impact of climate change in temperate and pluvious regions is less than other areas. The results of comparing the average annual rainfall in the past and the future for the stations show that the average rainfall in Gorgan station will decrease 8.6 percent up to 2100 on average; however, in Mashhad and Oroumieh it will have an increase of 40 and 32 percent respectively. Also in this research, wet and dry periods have been specified in future by comparing the long-term mean annual precipitation and 5-year moving average rainfall. The results show an alert on climate evolution that certainly has a direct impact on water resources and agricultural productions. Therefore, it is necessary to reduce the intensity of climate changes by reducing greenhouse gas emissions, and control unfavorable impacts of this phenomenon on water resources and agricultural products by using efficient methods of irrigation and proper use of water resources.