Wind and moist air are drawn by the prevailing winds towards the top of the mountains, where it condenses and precipitates before it crosses the top. The air, without much moisture left, advances across the mountains creating a drier side called the "rain shadow".
Mountains can have a significant effect on rainfall. When air reaches the mountains, it is forced to rise over this barrier. As the air moves up the windward side of a mountain, it cools, and the volume decreases. As a result, humidity increases and orographic clouds and precipitation can develop.
Powered by. A rain shadow is a patch of land that has been forced to become a desert because mountain ranges blocked all plant-growing, rainy weather. On one side of the mountain, wet weather systems drop rain and snow. On the other side of the mountain—the rain shadow side—all that precipitation is blocked.