Why is it always rainy in Addis Ababa?
Addis Ababa lies 9 degrees north of the equator at about 2300 metres in altitude. Its' mean annual rainfall is about 1090 mm, with an average daily  probability of rain of about 41%. The inter-tropical convergence zone in this part of East Africa is a little anomalous, but sufficient to bring long rains in July-August, and short rains in March-April. Given the altitude, latitude and synoptic climatology, there is nothing unusual about this rainfall, though as Kwinkunks points out, if you happen to hit an unusually wet 'long rainy season' it might seem unusually wet.