Even more rain is expected, state television said Thursday, after average rainfall in the affected areas this week was recorded as 51% higher than in the corresponding periods of previous years, and the largest since 1961.
State television showed images of half-submerged buildings and flooded streets in some of the worst-hit areas. Trains along the Beijing-Guangzhou railway were delayed after rising waters blocked a bridge in the southern province of Hunan, it added.
The latest episode has caused losses of 2.69 billion yuan ($392 million), with 126,100 hectares (311,600 acres) of farmland damaged and 1,600 homes collapsed, the Ministry of Emergency Management has estimated.
As many as 77,000 people had been evacuated, it added. The affected areas include the southern provinces of Hunan and Jiangxi, eastern Zhejiang, the southeastern province of Fujian, and the northern parts of the southwestern Guangxi region.
The first three areas are expected to be doused again in a fresh burst of torrential rain Friday and Saturday, weather officials said, along with the central province of Hubei, eastern Anhui and the province of Guizhou in the southwest.
The Yangtze River in Jiangxi is expected to exceed its warning level for the first time this year around Sunday, swelled by heavy rain that could last until Tuesday, state TV said.
Extreme weather is becoming increasingly frequent in China, with temperatures in some parts hitting records this year.
Weather officials warned on July 3 that rainfall in the south could surpass the average by 30% to 70% over a 10-day stretch.