I've been looking through some depictions of people like Musa I, Suleiman the Magnificent, Menelik II (photograph), and Akia the Great, these guys are wearing layers and layers of carpet-thick cloth. Given the climates they were from, this seems extremely impractical. Were these really part of their regular attire, or were they more ceremonial and thus something that they would have been depicted in?
I will note that some of these depictions are much more modern, like this one of Askia: http://www.anheuser-busch.com/s/uploads/Dillon_AMToure.jpg
But there are several depictions of Suleiman and this photo of Menelik where they really are decked out in very thick, extravagant garb.
Those are ceremonial yes(and worn by the emperor at that). That said, the region is by no means uniformly hot and dry and climate depends much on elevation, geography, etc. So certainly there would be times when dressing warmly would be advisable.
Arabs wove some of the finest fabrics so those thick looking clothes may have been quite comfortable. The common people wear long clothes because it keeps the sun off them and it traps sweat and moisture, helping them stay cooler than short sleeves and shorts.
