The four main climate zones of Africa are semi-arid, desert and arid, subhumid and humid. The largest is the desert and arid zone, which covers most of northern Africa. The wet period for that zone lasts just three months, which results in little to no vegetation.
The Sahel lies in the semi-arid zone just south of the desert and arid zone. It is slightly less hot, with a little more rainfall than the desert, so grasslands and savannas cover the zone. Humid areas are moist and tropical, and they are located in western and central Africa. Humid areas experience excess rainfall nine months of the year. Subhumid areas in south-central Africa are temperate, experiencing sufficient rainfall to grow crops with irrigation.