The east and south of Ethiopia consists of the Danakil Desert, the southern highlands (which includes Bale Mountains National Park), the Ogaden and the South Omo Valley.
The Danakil Desert, which includes the Danakil Depression, makes up the borderlands with Eritrea. With average temperatures of 35°C – there are days when temperatures exceed 48°C – and an average annual rainfall of between 100 and 200m, visits this far east make for hardy travelling indeed, and are best conducted between November and March, when temperatures drop to a sweltering average of 25 °C.
With an altitudinal range of 2013 to 4385m, and an annual rainfall of 1134mm, the Bale Mountains constitute the region’s wettest area. Rather, therefore, than experience - like the rest of the south - a double rainfall dip, the Bale Mountains are pretty much wet right through from March to October, and are best visited between November and February. Daytime temperatures at this time average out at around 16°C, while night temperatures hover between 2°C and 4°C, and can plummet to well below zero.
The picture with regards to the rest of the south is reasonably clear. The dry seasons occur from June through to September, and between November and March. There are two rainy seasons. The first of these - late March through to early June - is heavier, with the South Omo Valley and regions local to the Bale Mountains receiving between 200 and 250mm in April and the first weeks of May, the mid-south peaking at about 125mm, and Ogaden receiving 75mm at its very best. This pattern - the further south-east one travels, the drier it gets - is just as true later in the year, during the area’s second set of rains, when between September and November the likes of Hagere Marian (just north of South Omo) peak at around 180mm (October), while Gode in Ogaden barely gets above 50mm. Clearly, travel in the mid-south and south-east is hard going, with temperatures soaring into the late thirties, the heat dry, the habitats extremely arid. The South Omo Valley is also dry and hot, but, being in the Rift Valley, better watered and fairly comfortable during the dry seasons.