Situated between 37° north and 34° south, Africa mainly lies within tropics. Only the northern and southern tips have a Mediterranean climate. Africa is therefore a predominantly warm continent. The mean annual temperature is above 20°C throughout the tropics, and annual daily temperatures are only higher in the desert. The rains determine the climate. The equatorial climate extends over the Congo Basin, on either side of the equator. Temperatures are high and vary only slightly over the year (25°C on average). There is regular rainfall, totalling in excess of 1,500 mm, and sometimes as much as 2,000 mm.
The tropical climate is characterized by alternating dry and rainy season. The difference between the seasons becomes more marked the nearer o the tropics; similarly, there is a greater variation in temperatures and total rainfall decreases. Due to the size of the continent, the influence of latitude predominant in the northern hemisphere; there is a series of tropical belts parallel to the equator.
The wet tropical climate is similar to the equatorial climate in the c amount of rainfall, but there are two dry seasons of unequal duration (August and December to March in the northern hemisphere). This type of climate prevails along the Gulf of Guinea, from Sierra Leone to Cote d’Ivoire. In the Great lakes region, apart from on high ground, rainfall is less than 1,500 mm per annum. In the dry tropical, or Sudanese, climate, the dry season lasts longer (three to six months on average) the nearer one is to the tropics. The drought is accentuated by the harmattan, a dry, warm wind that blows towards the Atlantic. The wet season, known as the Hivernage, arrives when the sun reaches its zenith. The annual rainfall exceeds 1,000 mm in the south of Mali but remains below 800 mm to the north of Nigeria. The climate in the Sahel is affected by increasingly rare rainfall (less than 500 mm), which only occurs during a short period (three months at the most); there is also extreme irregularity from one year to the next. Temperatures, much higher than in the wet regions, can reach 40°C at the end of the dry season.
South of the equator, the seasons are the reverse of the northern hemisphere and the climate zones run from east to west. Arid and semi-arid zones are confined to the south-west, whereas the coastal strip along the Indian Ocean, to the southeast, has a very wet climate (monsoon). On average, temperatures are lower than in the northern hemisphere. These differences are linked to the proximity of the sea and the relatively high relief in the southern part of the continent. In Madagascar, the eastern side of the island is very wet as it is exposed to trade winds (over 2,000 mm of rainfall per year), as opposed to the western side which is “downwind” and much drier.
The desert region extends unevenly in both tropics. In the north, the Sahara covers over 8 million km2, whereas the Kalahari and the Namib occupy a less extensive area in southern Africa. Rainfall is frequently below 100 mm per year. High atmospheric pressure and cold sea currents result in drought that is accentuated by strong winds. Daily (up to 50°C) and annual (25 to 30°C) temperature variations are high.
A Mediterranean climate is confined to the northern and southern tips of the continent. Summers are warm and dry, winters mild and damp. Temperature deviations are greater inland, where frost and snow are frequent. In the Maghreb, the mean annual temperature is 18°C on the plains, but only 14°C in the Atlas Mountains.
Africa is affected by climate change that will have serious consequences on agricultural output and the health of the population (for example, lower and more irregular rainfall encourages greater numbers of disease-bearing insects and makes producing enough to eat yet more challenging).
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