Intermediate · 3 min
Mountains and rainfall
Moist air forced up a mountain slope often cools, allowing water vapor to condense and precipitation to fall. After crossing the ridge, descending air warms and its relative humidity falls. The downwind side can therefore be drier, forming a rain shadow.
Visual explanation
Across a mountain barrier
- Moist air rises on the windward slope
- Air cools; condensation and rain may occur
- Air descends and warms on the downwind side
The downwind side can be drier. Actual rainfall also depends on the available moisture, wind, and local conditions.
Simplified diagram. Read the explanation for the conditions and limits.