Shanghai has northern subtropical monsoon climate with four distinct seasons, sufficient sunshine and abundant rainfall. The climate is mild and humid, the spring and summer are short, and the winter is long. In 2009, the city's average temperature was 17.8 ℃, the sunshine duration was 1,506.5 hours, and the rainfall was 1,457.9 mm. Over 60% of annual rainfall is concentrated in the flood season from May to September.