The best time to visit the Moroccan Sahara is between October and April when daytime temperatures are bearable, however, in December and January night-time temperatures can plummet below freezing so you'll need to travel with suitable clothing. To experience the ethereal beauty of the Sahara sand dunes without the crowds, visit during the quietest months of November, January and February.
Temperatures are particularly fierce between June and August and therefore not ideal for the elderly or the very young though. During the height of summer, Moroccans come to Erg Chebbi to be buried neck-deep in the hot sand for a few minutes at a time. It's reputed that the power of the sands are a treatment for rheumatism.
The dunes are spectacular at any time of day but particularly impressive first thing in the morning with the rising sun and last afternoon as the sun begins to set and the sands blaze with changing colour.