The best time to visit is April to October, outside the coldest months. June to September are the wettest months when blocked roads and swollen rivers can make travel difficult but the countryside will be at its greenest. However, health considerations should be taken seriously at any time of the year, and even in relatively balmy Lhasa temperatures fall below freezing on a regular basis. In winter, as long as you come fully prepared for the cold (most hotels have no heating) and possible delays due to snow-covered passes, the lack of tourists and the preoccupation of the security forces with staying warm can make for a pleasant trip.