You might spend a lot of your vacation inside, but if you want to see more of the area, taking a look at local weather data can help you. The hottest months are usually August and July with an average temp of 78°F, while the coldest months are January and February with an average of 49°F. The rainiest months in Zhoushan are June, July, September, and May, with each month seeing an average of 9 inches of rainfall.