Shanghai has a monsoon climate of East Asia. It is bordered by sea in the east with a warm and humid climate and four distinct seasons. 
Light clothes like lined jacket and woolen sweater are suitable for the weather in Spring (from March through to the end of May) and Autumn (from September to November).
Extra-light clothing is for summer (from June to August).
Heavy woolen overcoats are necessary to keeping out the cold outdoors in winter (from December to February).
Since there is much rain during the periods between Spring and Summer and between Summer and Autumn, it is advisable to get rain gear ready.