Jamaica Geography & Climate

Jamaica is about 235 kilometres long and 80 across at its widest, in the Greater Antilles south of Cuba and west of Hispaniola. Most of it is limestone laid over a submerged mountain range, and that geology explains nearly everything about the island.

The Blue Mountain range runs along the eastern end and reach 2,256 metres at Blue Mountain Peak — high enough that the summit is cold at dawn and that coffee grown on its slopes commands the price it does. The John Crow Mountains sit behind them, wetter still.

The centre and west are Cockpit Country: a karst landscape of conical hills and steep sinkholes formed as water dissolved the limestone, almost impassable, largely uninhabited, and the island's principal water catchment. Its inaccessibility is precisely why the Maroons could hold it against the British army.

The coasts differ sharply. The north is lush and holds most of the resorts; the south coast around Treasure Beach sits in a rain shadow and is dry enough to grow cactus. Rivers run short and fast off the limestone, which is why there are so many waterfalls.

The Blue and John Crow Mountains are Jamaica's only UNESCO World Heritage site, listed for both their biodiversity and the Maroon heritage held within them.

Limestone and karst

Around two-thirds of Jamaica is limestone, laid down when the island was submerged and since uplifted and dissolved by rain into a landscape of sinkholes, caves and underground rivers. Its most extreme form is Cockpit Country in the west: a maze of steep conical hills separated by deep enclosed hollows, almost impossible to cross, which is exactly why the Maroons were able to hold it against British forces and win a treaty.

Mountains and rivers

A spine runs the length of the island, rising in the east to the Blue Mountain range at 2,256 metres. Short, steep rivers run off it in both directions, and the north coast’s rivers have cut gorges and produced the waterfalls the tourist industry is built on.

A tectonic setting

Jamaica sits on a complex boundary between the Caribbean and North American plates, which is why it has been struck by destructive earthquakes — Port Royal in 1692 and Kingston in 1907 — and why the terrain is as vertical as it is.

Jamaica is tropical maritime: coastal temperatures sit between about 26 and 32°C year-round, moderated by the trade winds, with high humidity.

Altitude changes everything. Kingston is hot; the Blue Mountain range is cool and wet, and Blue Mountain Peak before dawn can approach freezing. People climb it in shorts and regret it.

Rainfall is very unevenly distributed. The north-east around Port Antonio is among the wettest places in the Caribbean and is green because of it; the south coast around Treasure Beach sits in the mountains' rain shadow and is close to semi-arid.

There are two wetter peaks, in May and again from September to November, usually as heavy afternoon showers rather than continuous rain. Hurricane season runs June to November, with the highest risk from August to October.

Windward and leeward

The north-east trade winds strike the island’s mountain spine, so the north and east are wet and green while the south coast, in the rain shadow, is markedly drier — Kingston receives around 800 millimetres a year, while parts of the eastern hills receive several times that. It is the single most useful thing to understand about Jamaican weather, and it explains where the rainforest, the coffee and the cactus scrub each are.

Two wet peaks

Rain comes in May and again from September to November, with December to April the driest and most comfortable period. Showers are typically short and heavy rather than prolonged.

Hurricanes

The season runs June to November and peaks between August and October. Jamaica has been struck severely several times, and the practical consequences for a visitor are insurance, flexibility and attention to official warnings, which are issued well in advance.