The combination of southeastern trade winds and northwestern monsoons produces a hot rainy season (November–April) with frequently destructive cyclones, and a relatively cooler dry season (May–October). Rain clouds originating over the Indian Ocean discharge much of their moisture over the island's eastern coast; the heavy precipitation supports the area's rainforest ecosystem. The central highlands are both drier and cooler while the west is drier still, and a semi-arid climate prevails in the southwest and southern interior of the island.