It is still hot in Mid Spetember. You can wear T-shirt and summer trausers. Bring a light jacket. It is cool in mountains and forests. For pearls, if you will visit Beijing, you can by in Hongqiao Pearl Market beside The Temple of Heaven (East Entrance). In Shanghai, there are brand stores or other small stores selling pearls around Yuyuan Garden. Remember bargain in market and small stores. The price is set in brand stors which can assure the quality. You can also ask if there is discounted price. If possible, you can learn somthing about how to distinguish real and fake, good and bad pearls.