Hi, what type of clothing to bring if I am going to Shang Hai, Hang Zhou & Su Zhou during Christmas?

yes, need to wear long johns. Or you can wear t shirt and down coat, or coat plus sweater. A few layers of t shirt plus a warm jacket will do either. If there is cold air, it may snow in this cities. The temperature may fall nearly to zero. If the weather is warm, it may be 10 degrees. You can prepare clothes according to these temperature data.