The islands form a large arc extending eastwards from the Yucatán peninsula of Mexico and the Florida peninsula of the United States. The larger islands are, from west to east: Cuba, Jamaica, Hispaniola (divided into the two separate political units of Haiti and the Dominican Republic), and Puerto Rico. To the north of these larger islands lies a group of small scattered islands: the Bahamas and the Turks and Caicos Islands. East of Puerto Rico the chain of islands curves southwards as the Lesser Antilles, terminating in Trinidad, which is close to the coast of Venezuela. The Lesser Antilles are often divided into the Leeward Islands group in the north and the Windward Islands group in the south.

Despite the large area over which these islands are scattered, there is a strong similarity of weather and climate everywhere. The waters of the Atlantic Ocean and the Caribbean Sea are warm at all times of the year, being influenced by ocean currents from equatorial latitudes which unite to form the Gulf Stream to the north of the Caribbean. The area lies for the whole year under the influence of the northeast trade winds, or the North Atlantic anticyclone which lies farthest south in the winter period.

Almost everywhere the wettest months are from May to October and the winter period is relatively, but by no means completely, dry. The area experiences no great extremes of temperature; winters are warm and sunny and summers are hot, but without excessively high temperatures so that heat stress is rarely felt. Almost nowhere in the Caribbean have maximum temperatures above 100°F/38°C been experienced, and only in Cuba and the northern islands of the Bahamas do winter temperatures occasionally fall much below 60°F/15°C. This equability of temperature is a consequence of the strong influence of the warm sea. Waves of cold air from North America in winter and spring affect only western Cuba and the northern Bahamas for a few days, and the air arriving in the islands may be as much as 10°–15°F/5°–8°C warmer than when it left the coast of the mainland.

Most of the larger and many of the smaller islands are mountainous, and this gives rise to numerous local differences of weather and climate. Apart from the fall of temperature with altitude, there is often a big increase of rainfall on the mountains; and the northern and eastern slopes and coasts of the islands are usually considerably wetter than the southern and western sides, which are sheltered from the persistent northeast trade winds. Unfortunately most of the climatic data available for the West Indian islands is from places at or near sea level, but a good example of the increase of rainfall with altitude can be seen by comparing the table for Camp Jacob on the islands of Guadeloupe with that for Plymouth on the nearby island of Montserrat – both in the Leeward Islands. Camp Jacob, at an altitude of 530 m/1,750 ft, has more than twice the annual rainfall of Plymouth. It is known that annual rainfall on the highest mountains in Cuba and Jamaica is two or three times that of the places at sea level for which tables are given in this book. In these wetter mountain areas cloud is more frequent than at sea level at all times of the year.

The Caribbean Islands have developed an important tourist trade, and one reason for this is the large number of hours of sunshine around the year. Daily sunshine hours average from seven to nine, with more in the driest months. The winter months are the driest and sunniest and, at this time, the slightly lower temperatures are made more pleasant by frequent sea breezes and lower humidity. Even in the warmest months the combination of temperature and humidity is rarely very uncomfortable if moderated by a strong breeze. The tables show that some places have a large number of days with rain; as many as one in two or one in three. This should not be taken to imply that it rains all day; on many days cloud builds up in the afternoon to give short thundery showers in the late afternoon and evening. Prolonged spells of rain are rare and are usually associated with hurricanes or tropical storms, which are the worst features of the weather and climate of the Caribbean.

Hurricanes occur between June and November and are most frequent in the months of August and September. During the worst of these storms 250–500 mm/10–20 in of rain may fall over a period of two or three days and the very violent winds may cause damage. Individual islands may go several years without experiencing a severe hurricane and, on the larger islands, their worst effects may be confined to only one area. Over the area as a whole, however, some two to three hurricanes may occur each year. They develop east of the Caribbean and move westwards before curving north and east close to the North American mainland. A significant proportion of the rainfall in the months August to October may be caused by hurricanes since places which escape the centre of the storm with its damaging winds may be affected by the cloud and heavy rainfall on the fringe. Tropical storms which do not develop to full hurricane intensity may bring a period of two or three days of cloud and rain.