Hawaii's Rainfall Extremes: From Arid Coasts to the Wettest Mountain Slopes

Annual Precipitation in Hawaii

Hawaii's rainfall varies dramatically over short distances due to topography and trade winds.

• Leeward (dry) coasts: As little as 10 inches (250 mm) per year.
• Windward (wet) mountain slopes: Over 200 inches (5,000 mm) on Mauna Kea, Mauna Loa, and Haleakalā.
• Example – Maui: Windward Haleakalā slopes receive 100–125 inches; leeward areas get <5 inches.

This extreme gradient creates diverse ecosystems—from desert-like coastal zones to lush rainforests—within a single island.