Spring (April–June) and autumn (September–November) are the best seasons. The mountain air is cool, the countryside is green, and the rice terraces are at their most photogenic. Summer (July–August) brings the largest crowds and the hottest temperatures, though the heat inside the thick earthen walls is considerably less than outside — the building design maintains a surprisingly stable interior temperature. Winter is cold in the mountains (the tulou sit at moderate altitude) but nearly empty of tourists, and the morning mist on the valley floor at sunrise in January is one of the most atmospheric images the area produces.