The summer crowds would not have swarmed down yet, and the weather is mild. Winter can be bitterly cold with temperatures dipping well below zero and a drizzle is never far.
Summer is scorchingly hot.
Avoid travelling to China during major holidays as all businesses come to a standstill. Tourist attractions are also closed. If you want to go mountain climbing, the best time is in autumn and spring when the humidity is low. The peak tourist season is from May to October. Be forewarned that the weather can be quite unpredictable.