The ecoregion's climate is humid subtropical, in middle altitude locations, oceanic and in the mountains, humid continental with most precipitation occurring in fall, winter, and spring. The Alborz mountain range is the highest mountain range in the Middle East which captures the moisture of the Caspian Sea. Annual rainfall ranges from in the east to in the west, making this ecoregion much lusher than the desert, semi-desert, and steppe ecoregions on its borders.