We've just returned from 3 weeks Morocco, the spring rains gave the country an absolute delightful appearance, with the desert blooming and happy people smiling in the rain.
That rain did however turn to snow in the High Atlas, preventing us from doing a part of the trip.
We also experienced some trouble with flooded roads and vanished bridges.
All the more adventure though, compared to the time I visited Morocco after a dry summer.
So, all 'n all, I'd say spring is your best option.
Landrover Discovery 2 Td5 with a Garmin 276c and a great co-driveress