Here's how it works:
* Moist air rises: As moist air approaches a mountain range, it is forced to rise.
* Cooling and condensation: As the air rises, it cools, causing the water vapor it contains to condense into clouds and precipitation.
* Dry air descends: The air that descends on the other side of the mountain range is now drier, having lost much of its moisture on the windward side.
* Warming and less precipitation: The descending air warms, making it less likely to condense and produce precipitation. This results in a drier climate on the leeward side of the mountain range.