In reply to emdawes:
I had a great trip there September 2010. Climbing from the valley to the north side of Jebel el Kest gives lots of opportunities for shaded climbing. Topping out for warm sunset as the heat of the day dispersed was lovely.
In contrast, the air temp in the spring can be cold relative to the sun, so that you need to wear fleeces in the shade, but still bake in the sun.
Watercourses were low in September after the summer, making access to e.g. Waterfall Walls easier.
On rest days we lay behind trees in the breeze or looked for swimming holes, still pretty hot in the sun, so wouldnt recommend any south facing rock (they hold many more scorpions, snakes and toxic plants too, anyway...)
Have fun!