September is one of the best months for travelling in China. With comfortable temperatures of around 15-26 degrees Celcius (59-79 degrees Fahrenheit) in Beijing and around 21-27 degrees Celcius (70-81 degrees Fahrenheit) in Shanghai, touring the two major Chinese cities is pleasant and not as congested as the summer months. There is little rain and humidity levels are low.
The rest of the country is also generally quite dry and if you are travelling to south China, this is a great month as you will miss the peak tourist season and avoid the intense and humid heat. There is still a great deal of tourists at the most popular destinations, but as schools and universities start after the summer holidays, domestic travel will have lessened by September.
If you are in China during September, don't miss the Mooncake Festival, also known as the Mid-Autumn Festival, a Chinese harvest festival and celebration of the moon. Popular eats include a round pastry with lotus seed filling known as a mooncake.