I have read about potential precipitation increases across East Africa, though I remain sceptical given the fact that the opposite trend is happening.
However, I don't know where you got the information about decreased average temperature?
Give it time, globally we’re at a ~1° degree increase which no models have predicted will increase precipitation. Also, the latest models predict this effect
mainly in Somalia IIRC with opposite or uncertain changes elsewhere.
Woodlands and thickets decrease temperatures through a process known as evapotranspiration and also provides shade and carbon sequestering. The effect can be so dramatic as to cool an area locally by 2-4° degrees compared to open plains or bare urban areas. This is a geographically limited effect though. Might just end up being a net neutral with the warming in mind, but I’m optimistic.