Ningbo, where it's located

The climate of Ningbo is temperate, with relatively cold winters and hot, muggy, and rainy summers. Ningbo is a metropolis located in eastern China, in the Zhejiang Province, on the East China Sea coast, south of the Hangzhou Bay and a short distance from the Zhoushan Archipelago. 150 km (95 mi) north of the city, we find Shanghai.
Here are the average temperatures.
Ningbo - Average temperatures
Min (°C)2361117212525211594
Max (°C)91014202528333228231812
Min (°F)363743526370777770594839
Max (°F)485057687782919082736454

Rainfall is quite abundant, and amounts to 1,400 millimeters (57 inches) per year. There is no real dry season; nevertheless, rainfall is below 100 mm (4 in) per month from October to February. Summer, a season when the rains occur mainly in the form of showers or thunderstorms, is the rainiest season, especially in June, when the sun is rarer as well. Here is the average rainfall.
Ningbo - Average precipitation

Winter, from December to February, is quite cold: the average January temperature is 5 °C (41 °F). There may be cold periods, with highs around 5 °C (41 °F) or below, when even light snowfalls are possibile. In other periods instead, the temperature becomes mild, around 15 °C (59 °F). Sunny days are a bit more frequent in December, then they become rarer.

Spring, from March to May, is initially mild, and then becomes gradually warmer. In May, there are already some hot, summer-like days.

Summer, from June to September, is hot and muggy. The heat island effect of the large city and the humidity make the heat unpleasant, especially in July and August. Fortunately, the breeze blows from the sea. June is the rainiest month of the year. Periods of good weather can be sweltering, especially in July and August, with highs around 37/38 °C (99/100 °F) or higher, and tropical nights.

Autumn, in October and November, is initially mild, and gradually becomes cooler, and then quite cold at night by November. Rainfall is moderate.

Tianfeng tower

The amount of sunshine in Ningbo is not very good; however, it is slightly better than on other Chinese cities located at a greater distance from the coast; in July and August, it is decent, while it is poorer from January to June.
Ningbo - Sunshine

Near Ningbo, the sea (East China Sea), cold in winter, becomes warm enough for swimming from July to September; in June and October, it is a bit cool but basically acceptable.
Ningbo - Sea temperature
Temp (°C)121011141923272826232015
Temp (°F)545052576673818279736859

From time to time, from June to early November, typhoons, the tropical cyclones of Southeast Asia, can affect this area, though less so than in southern China.

Best Time

It is not easy to find the best time to visit Ningbo. As the spring is more rainy, you can choose autumn, especially from the end of September to the beginning of November, which is generally a mild or pleasantly warm period; it must be said that the arrival of a typhoon can not be excluded.