From Mar. to Apr. At this time, temperature is around 10C/50H-25C/77H. We usually wear sweaters, suits and shirts during Spring.
From Jun.-Aug. Temperature is around 25C/77H-35C/95H in summer. And it is the rain time in Yiwu, rain occurs day in and day out, so umbrella is necessary, and normally you can get from hotel. Clothes mainly are shorts, thin shirts and skirts, bonus would be sunglasses and sun creams.
From Sep.-Nov. Temperature would be 10C/50H-25C/77H. Wear any clothes you like with this temperature.
Dec.-Feb. Temperature here:0C/32H-10C/50H, sometimes below zero. So you would need thick clothes like big coat and long johns. Also, those things which can keep you from cold, like warm socks, scarf and gloves, would be your good protector in winter.