With a pleasant northern subtropical maritime monsoon climate, Shanghai enjoys four distinct seasons, generous sunshine and abundant rainfall. Its spring and autumn are relatively short compared with summer and winter. The average annual temperature is 18 degrees Celsius. The city has a frost-free period lasting up to 230 days a year. The average annual rainfall is 1,200 millimetres (about 50 inches). However, nearly 60% of the precipitation comes during the May-September flood season, which is divided into three rainy periods, the Spring Rains, the Plum Rains and the Autumn Rains.