The climate of East Africa is rather atypical of equatorial regions. Because of a combination of the region’s generally high altitude and the rain shadow of the westerly monsoon winds created by the Rwenzori Mountains and Ethiopian Highlands, East Africa is surprisingly cool and dry for its latitude.
The lower-lying lands of northern Kenya and Greater Somalia are indeed extremely dry. In fact, on the coast of Somaliland and Punt land many years can go by without any rain whatsoever. Elsewhere the annual rainfall generally increases towards the south and with altitude, being around 400 millimeters (16 in) at Mogadishu and 1,200 millimeters (47 in) at Mombasa on the coast, whilst inland it increases from around 130 millimeters (5 in) at Garoowe to over 1,100 millimeters (43 in) at Moshi near Kilimanjaro. Unusually, most of the rain falls in two distinct wet seasons, one centered on April and the other in October or November. This is usually attributed to the passage of the Inter-tropical Convergence Zone across the region in those months, but it may also be analogous to the autumn monsoon rains of parts of Sri Lanka, Vietnam and the Brazilian Nordeste. West of the Rwenzoris and Ethiopian highlands the rainfall pattern is more typically tropical, with rain throughout the year near the equator and a single wet season in most of the Ethiopian Highlands from June to September – contracting to July and August around Asmara. Annual rainfall here ranges from over 1,600 millimeters (63 in) on the western slopes to around 1,250 millimeters (49 in) at Addis Ababa and 550 millimeters (22 in) at Asmara. In the high mountains rainfall can be over 2,500 millimeters (98 in).
Rainfall in East Africa is influenced by El Niño events, which tend to increase rainfall except in the northern and western parts of the Ethiopian and Eritrean highlands, where they produce drought and poor Nile floods.[21]
Temperatures in East Africa, except on the hot and generally humid coastal belt, are moderate, with maxima of around 25 °C (77 °F) and minima of 15 °C (59 °F) at an altitude of 1,500 meters (4,921 ft). At altitudes of above 2,500 meters (8,202 ft), frosts are common during the dry season and maxima typically about 21 °C (70 °F) or less.
