Generally speaking, if you’re travelling in summer (June, July and August) you can expect it to be hot, hot, hot – no matter where you are. When packing, make sure you’ve a couple of hats, loose-fitting pants and t-shirts and some long-sleeve shirts for extra protection from the sun.
If you’re travelling in the Chinese interior (Chengdu, Hunan, Xi’an) the summer weather will usually be dry, but if you’re near the coast (Shanghai) or in the south (Yangshuo) you can expect some summer storms. It’s a good idea to pack a lightweight raincoat and waterproof shoes if you’re in either of these regions.