Since average annual temperatures are high nearly everywhere in Africa, division of the continent into climatic regions is based chiefly on amount and seasonal distribution of rainfall. Seven main types of climate affect the continent. Four are tropical, ranging from arid to extremely wet; they cover at least three-fourths of Africa. The other three are subtropical to temperate.
The tropical rainy climate exists in only a comparatively small part of Africa. It occurs in a band 700 miles (1,100 km) wide along the Equator, ending at the highlands of east-central Africa. There are also narrower belts along the Gulf of Guinea, which has strong monsoonal influences, and along the east Madagascar coast. These areas are extremely humid, though not excessively hot. Temperatures remain near 80° F. (27° C.), with little variation seasonally and from day to night. All months are rainy, some more so than others. Annual amounts of precipitation vary from 60 inches (1,500 mm) inland to 130 inches (3,300 mm) or more along the coasts.
Away from the Equator rainfall decreases and a distinct dry season develops during the cooler parts of the year —the period when the sun is on the opposite side of the Equator. Lasting as long as six months, the dry period is this climate's most distinguishing feature. Rainfall totals 20 to 60 inches (500 to 1,500 mm) a year. There is a slightly greater seasonal range in temperature here than in the tropical rainy regions. Much of eastern and southern Africa has a modified savanna climate, with slightly lower temperatures because of increased elevation. This kind of climate is typical of regions with savanna-type vegetation.
Bordering the tropical savanna is the tropical steppe climate. It is more seasonally extreme in both temperature and rainfall than is the savanna. The warmest month averages more than 85° F. (29° C.), the coolest as low as 60° F. (16° C.). Average annual rainfall varies from 10 to 20 inches (250 to 500 mm).
A relatively large part of Africa has a tropical-desert type of climate. In such a climate, temperature ranges are greatest, for the bare to sparsely covered land heats and cools rapidly under cloudless skies. Daytime temperatures during the hotter months often exceed 100° F. (38° C.); occasionally they rise above 130° F. (54° C.). The coolest month averages 50° to 60° F. (10° to 16° C.) during the day, though freezing weather may occur at night. Average yearly rainfall does not exceed 10 inches (250 mm) anywhere; some areas go without rain for years.
Mild average annual temperatures, dry summers, and moderately rainy winters are the chief marks of the Mediterranean climate. It occurs along part of the northern and southern coasts, where climatic influences from the middle latitudes are felt. During the warmest month temperatures average slightly above 70° C. (21° C.) near the coast and about 80° F. (27° C.) inland. Temperatures for the coolest month are roughly 50° F. (10° C.) and 60° F. (16° C.), respectively. The annual rainfall is about 20 to 30 inches (500 to 750 mm.)
Part of the southeastern coast has a humid subtropical climate, which in temperature is similar to the Mediterranean type. Yearly rainfall, however, reaches 40 to 60 inches (1,000 to 1,500 mm) and is concentrated in the summer rather than the winter months.
In the highland regions, especially the loftiest sections of eastern Africa, temperatures are much lower than in areas of comparable latitude at lower elevations. This is particularly true in the Ethiopian Highlands and in some of the Rift Valley mountains. In areas of sharp relief lying in the path of moisture-bearing winds, rainfall is heavy.