I'm going to travel to beijing at May, and I don't know how I should wear in that season

Hi, the average temperature in May can be around 20C. I suggest you take along long-sleeved T-shirt or shirt plus long jeans in case of the morning and evening coolness. For the sunny afternoon, dress and shorts may be needed. Besides, a light coat will help in case of weather changes.

As I know, most of the shopping malls are open from 10:00 to 22:00 every day.