Hi Pauline, I'm afraid I'm not doing this tour so probably won't be much help. I wasn't going to answer, then I saw you didn't have any replies (this might have changed by the time this appears), so thought I'd throw in a few comments. The best thing you can do is google the climate in the main places you'll be visiting - Beijing, Shanghai etc as China is a huge country, I imagine the climate will vary a bit from place to place. However, I'd say it would be warm to hot in most places and probably quite humid as well - so lightweight clothes t shirts, shorts etc with warmer clothes for the evenings. Don't forget to check if you need DEET, insect repellent etc for the places you'll be visiting. Hope this helps!
Bob