Visit between October and April. The Sahara summers are brutal — Erfoud sees average highs above 40 °C in July and August, with sandstorm conditions not uncommon, and most of the desert excursions from town become unpleasant or unsafe. October to early November is the date harvest, with the Festival des Dattes taking over the centre for a long weekend of music, processions, and tasting.
December and January are cold at night — drop close to freezing in the dunes — but the days are crisp and the light is at its best. February through April is the most reliable window: warm days, cool nights, clear skies, and dunes still in their winter colour.