Strongly affected by the sea, the region has a humid climate without winter chilliness and summer heat. Zhoushan has a four-season, monsoon-influenced humid subtropical climate, with cool, damp winters, and hot, humid summers. Typhoon may concentrate on the period from July to September. The best time to pay a visit is during June to October.
Zhoushan is generally moderated by the surrounding waters of the East China Sea, bringing a an average temperature of 5.8 °C (42.4 °F) in January and 27.1 °C (80.8 °F) in August, hence an annual mean of 16.43 °C (61.6 °F).
Precipitation is significant throughout the year, with the greatest rainfall during summer. With 1,938 hours of bright sunshine annually, ranging from 34% sunshine in March to 56% in July, the second half of the year is sunnier.