Topography Impacts Climate
Arid regions and rainforests are sometimes to be found on opposites sides of mountain ranges. Before clouds can pass to the other side of the mountain, they must dump their heavy load of moisture onto the ground. Then they are light enough to rise over the mountain and pass to the other side.
Thus, often, the fore side of the mountain range receives a lot of rain, and the lee side receives little rain. This phenomena is part of the regional climate of regions of the Earth's surface.