Here's why:

* Orographic Lift: When moist air masses encounter a mountain, they are forced to rise. As the air rises, it cools, causing the water vapor to condense and form clouds and precipitation.

* Rain Shadow: The side of the mountain facing the wind (the windward side) receives the majority of the precipitation. The air that passes over the mountain is now dry, creating a rain shadow on the leeward side.

So, the leeward side, also known as the downwind side, is typically drier than the windward side.