Sichuan, Hunan, Hubei, Jiangxi, Anhui

Joao, it's autumn from September to November. Generally speaking, it's fine for you to visit these regions. You can wear thin outer garment, long sleeved T shirt and jeans. However, if you plan to visit Jiuzhai Valley and Aba Area in Sichuan, I think you may bring some thick clothes because it's a bit cold due to the high altitude. It would be much better if you could have specified which cities you are going to visit. Then I can try to help you find out what exactly you should wear.