Why is it so humid inside the riad?

A riad is built around an open central courtyard — the wast al-dar. Rain falls into it. The fountain runs into it. The citrus tree gets watered into it. Every bedroom door opens onto that air, not onto a corridor, so there is no humidity barrier between the courtyard and the bed. By morning the towels are damp.

The walls compound it. Traditional construction is rammed earth or fired brick, finished in tadelakt — a polished lime plaster the Almohads were already using in the 12th century. Tadelakt breathes. It absorbs moisture from the air in winter and releases it slowly back, which is exactly what you want in summer at 45°C and exactly what makes January feel like a damp cave. Drywall would fix it. Nobody uses drywall.

Then the geology. Marrakech sits on a high water table fed by Atlas snowmelt, and the medieval city was watered by a network of khettara — underground channels engineered around 1078. Many medina houses are built directly over wells. Floor tiles laid on a bed of sand wick whatever rises. The rainy season runs November to March; in an unheated riad the indoor humidity in those months commonly sits between 70 and 85 percent. Hang nothing you need to wear the next day.