In general, visitors to China should pack casual, comfortable attire. Shorts are acceptable attire for most activities. Comfortable and durable walking shoes are essential since there will be much walking.

In spring (March to May) and autumn (September to November) you may need a linen jacket or woolen sweater as over-light clothing.
In summer (June to August) cool cotton garments are recommended.
In winter (December to February) a light cotton-patted coat will keep you warm enough in the south; but in the north a heavy woolen coat or down parka is a must.

Late spring and late summer are often rainy, especially in the southern part of China, so it would be wise to bring some wet weather gear with you.