Geography of Jamaica - Climate

Climate

Two types of climate are found in Jamaica. An upland tropical climate prevails on the windward side of the mountains, whereas a semiarid climate predominates on the leeward side. Warm trade winds from the east and northeast bring rainfall throughout the year. The rainfall is heaviest from May to October, with peaks in those two months. The average rainfall is 1,960 millimetres (77.2 in) per year. Rainfall is much greater in the mountain areas facing the north and east, however. Where the higher elevations of the John Crow Mountains and the Blue Mountains catch the rain from the moisture-laden winds, rainfall exceeds 5,080 millimetres (200 in) per year. Since the southwestern half of the island lies in the rain shadow of the mountains, it has a semiarid climate and receives fewer than 760 millimetres (29.9 in) of rainfall annually.

Temperatures in Jamaica are fairly constant throughout the year, averaging 25 to 30 °C (77 to 86 °F) in the lowlands and 15 to 22 °C (59 to 71.6 °F) at higher elevations. Temperatures may dip to below 10 °C (50 °F) at the peaks of the Blue Mountains. The island receives, in addition to the northeast trade winds, refreshing onshore breezes during the day and cooling offshore breezes at night. These are known on Jamaica as the "Doctor Breeze" and the "Undertaker's Breeze," respectively.

Jamaica lies in the Atlantic hurricane belt; as a result, the island sometimes experiences significant storm damage. Powerful hurricanes which have hit the island directly causing death and destruction include Hurricane Charlie in 1951 and Hurricane Gilbert in 1988. Several other powerful hurricanes have passed near to the island with damaging effects. In 1980, for example, Hurricane Allen destroyed nearly all Jamaica's banana crop. In recent years, Hurricane Ivan (2004) swept past the island causing heavy damage and a number of deaths; in 2005, Hurricanes Dennis and Emily brought heavy rains to the island. A Category 4 hurricane, Hurricane Dean, caused some deaths and heavy damage to Jamaica in August 2007.

The first recorded hurricane to hit Jamaica was in 1519. The island has been struck by tropical cyclones regularly. During two of the coldest periods in the last 250 years (1780s and 1810s), the frequency of hurricanes in the Jamaica region was unusually high. Another peak of activity occurred in the 1910s, the coldest decade of the 20th century. On the other hand, hurricane formation was greatly diminished from 1968 to 1994, which for some reason coincides with the great Sahel drought.