Physical Geography

Puerto Rico lies on the crest of a largely submerged volcanic mountain range and is crossed from east to west by low mountains. Roughly three-fourths of the island is either mountainous or hilly. The major range is the Cordillera Central, site of the island's highest peak---Cerro de Punta---which rises 4,389 feet (1,338 m) above sea level. Narrow coastal plains, somewhat wider on the north coast than on the south, extend around most of the island.

Rivers are generally short, swift, and shallow; consequently, they are of limited use. Most of the larger ones, including the Arecibo, La Plata, Manatí, and Loíza, flow northward to the Atlantic Ocean from the mountains. All the island's lakes and reservoirs are small.

The climate is generally mild, with temperatures averaging near 80° F. (27° C.) in July and 75° F. (24° C.) in January. Mountain areas are somewhat cooler. Rainfall is brought mainly by moist northeasterly trade winds. Areas north and northeast of the mountains receive an annual average rainfall of 60 to 70 inches (1,520 to 1,780 mm), while much of the south receives less than 30 inches (760 mm). The southwest is the driest part of the island. Some of the higher northern slopes receive more than 100 inches (2,540 mm). Occasional hurricanes do considerable damage.

The island was once heavily forested, but only small parts of the original forests still exist. Most of these are in the Caribbean National Forest, in eastern Puerto Rico. Palm trees and mangrove swamps line part of the coast. Hibiscuses, orchids, poinsettias, and bougainvilleas are among the island's many colorful plants.

Native animals include some 200 species of birds. The mongoose was imported to destroy pests but is now one itself. Marine life, including many kinds of tropical fish and coral, is abundant.