Potential evapotranspiration is one of the primary factors controlling the distribution and development of vegetation on a regional scale, especially in dry and semidry climates. Due to the importance of potential evapotranspiration, we survived 41 synoptic stations of the country under future climatic conditions and under current conditions (2017) for 2025, 2050, 2075 and 2100. The methods for calculating potential evapotranspiration according to the type of input data (temperature, relative humidity, wind speed, precipitation, geographical coordinates and altitude of each station) include seven hybrid methods based on Penman, two temperature methods, three hybrid radiation-temperature methods and a radiation method. Then, Agro-ecological Zonation (AEZ) was used to classify the country's stations. Based on the results, the maximum value of ETref in 2017 was at Chabahar study (14.56 mm per day) and Abadan (13.38 mm per day) study and the lowest value of ETref was at Bandar Anzali and Rasht stations (2.08 and 2.67 mm per day) respectively. In 2100, for ultra-arid climate, the average precipitation and ETref will be 121.3 and 4238 mm per year, respectively, which will have a reduction of 3.63 percent in precipitation and 1.81 percent for ETref, respectively, compared to their average in the same period of 2017. The country's average precipitation of arid climate in 2075 was 120 mm per year, the average potential evapotranspiration was 4193 mm per year.
