Smallest and easternmost of the Greater Antilles, Puerto Rico is bounded by the Atlantic Ocean on the north and the Caribbean Sea on the south. Mona Passage to the northwest separates the island from the Dominican Republic, and the Virgin Islands lie to the east. Puerto Rico is crossed by mountain ranges, notably the Cordillera Central, which rises to 4,389 ft (1,388 m) in the Cerro de Punta. Although rivers are short and unnavigable, some provide irrigation or hydroelectric power. The climate is mildly tropical, with little seasonal change. Rainfall is plentiful, despite some arid regions in the south. Hurricanes are likely to occur between August and October. In addition to the capital, other important cities are Ponce, Caguas, and Mayagüez.