Wanderlust World Wanderlust World The primary climatic difference between windward and leeward mountain slopes is rainfall.
Moist prevailing winds hit the windward side, forcing air upward. As it rises, it cools adiabatically, condensing moisture into heavy rain or snow. Once over the summit, the air descends on the leeward side, warming adiabatically, which evaporates moisture and creates a "rain shadow" with much drier conditions.
This orographic effect drives stark contrasts: lush forests on windward slopes, arid deserts on leeward sides—e.g., Hawaii's windward Hilo (wet) vs. leeward Kona (dry), or the wet western Cascades vs. dry eastern Washington.