Why is it so cold inside in winter?
The short answer
Thermal mass works both ways. The walls that keep riads cool in summer absorb cold in winter and radiate it inward. Marrakech nights drop to 5–8°C from November through February.
Rammed earth, stone, tadelakt — these materials absorb whatever temperature surrounds them. The courtyard that ventilated in July becomes a funnel for freezing air. The zellige floors become an ice rink.
Traditional riads weren't built with heating. Retrofitting radiators into 200-year-old walls is expensive and complicated. Many still rely on portable heaters.
Well-managed riads now have underfloor heating, proper radiators, heated towel rails, double glazing. The heating question is how you tell a cared-for riad from one that's merely decorated.
Upper-floor rooms are warmer. South-facing rooms with direct sunlight are best. A hammam in January is a rescue mission.