The first round of plum rain fell in Shanghai last night — nine days early — as the region marks the start of a period known for sultry, rainy weather.

This week, colliding air systems over the middle and lower reaches of the Yangtze River will form a “plum rain belt.”

Thundershowers hit the city yesterday night and are expected to continue today. Some areas could get up to 50 millimeters of rain.

The week will see showers and thunderstorms, with the mercury ranging from 24 to 31 degrees Celsius.

Wet conditions will linger for at least the next 10 days, the weather bureau says.

Shanghai’s plum rain season usually lasts 23 days, with average rainfall of 243.1 millimeters, nearly one-fifth of the year’s total rain.

The bureau warns residents to carry an umbrella over the coming days and to be careful of food going mouldy.

Furthermore, the damp weather could create risks involving electrical appliances.