with a mean of at Cherrapunji, in Meghalaya, India. The two distinct rainy seasons of the equatorial zone, where the sun is vertical at half-yearly intervals, become gradually merged into one in the direction of the tropics, where the sun is overhead but once. Snow falls on all the higher mountain ranges, and on the highest the climate is thoroughly Alpine. The countries bordering the Sahara are much exposed to a very dry wind, full of fine particles of sand, blowing from the desert towards the sea. Known in Egypt as the khamsin, on the Mediterranean as the sirocco, it is called on the Guinea coast the harmattan. This wind is not invariably hot; its great dryness causes so much evaporation that cold is not infrequently the result. Similar dry winds blow from the Kalahari Desert in the south. On the eastern coast the monsoons of the Indian Ocean are regularly felt, and on the southeast hurricanes are occasionally experienced. Health The climate of Africa lends itself to certain environmental diseases, the most serious of which are: malaria, sleeping sickness and yellow fever. Malaria is the most deadly environmental disease in Africa. It is transmitted by a genus of mosquito (anopheles mosquito) native to Africa, and can be contracted over and over again. There is not yet a vaccine for malaria, which makes it difficult to prevent the disease from spreading in Africa. Recently, the dissemination of mosquito netting has helped lower the rate of malaria. Yellow fever is a disease also transmitted by mosquitoes native to Africa. Unlike malaria, it cannot be contracted more than once. Like chicken pox, it is a disease that tends to be severe the later in life a person contracts the disease. Sleeping sickness, or African trypanosomiasis, is a disease that usually affects animals, but has been known to be fatal to some humans as well. It is transmitted by the tsetse fly and is found almost exclusively in Sub-Saharan Africa. This disease has had a significant impact on African development not because of its deadly nature, like Malaria, but because it has prevented Africans from pursuing agriculture (as the sleeping sickness would kill their livestock). Extreme points See also List of national parks in Africa Outline of Africa#Geography of Africa The Horn of Africa Richard Grant 2014. Africa. Geographies of Change. New York: Oxford University Press. Notes edward External links Geology of Africa