The Leeward side of a mountain range is in fact in a rain shadow. A rain shadow is an area of elevation where little to no rain falls, due to precipitation being forced out of passing clouds on the windward side of the mountain. Precipitation condenses as clouds rise over the mountain, and in general it precipitates as it crests over the mountain, leaving no moisture for the leeward side. An example of this is the American west, just west of the Rockies, where little to no rain falls.
