The worst hit region was the southern province of Hunan, where the death toll rose to 75 people on Sunday, with 46 missing, the official Xinhua News Agency said.
Three days of torrential rains last week washed away mountain villages in Hunan and damaged tens of thousands of homes, schools and other facilities in cities, Xinhua said. Inundated roads and highways hampered rescue and evacuation efforts, it said.
More than 200,000 people have been evacuated, Xinhua said.
State television showed footage of farmers removing debris from swollen rivers, evacuees camped out in blue tents and aid workers carrying boxes of emergency supplies. Residents waded through murky thigh-high water in some city streets.
Government figures put the estimated economic loss in Hunan at $2.3 billion yuan, about $277 million in U.S. dollars.
Another 17 have been reported dead in Guizhou and four in Sichuan.
China's rainy season officially began Wednesday.
According to government statistics, the floods this year have already killed 204 and left 79 missing, Xinhua said.
Last year, more than 1,300 people were killed in summer flooding. The government is forecasting heavier rains this summer.
Crops were deluged in the southern Chongqing region after 12 hours of continuous rainfall beginning Friday night, which also destroyed scores of homes and caused numerous landslides, Xinhua said.
Authorities in one county dispatched 51 buses to transport more than 2,000 passengers stranded at the Qijiang Railway Station on their way to Chongqing, Xinhua said.
Vice Premier Hui Liangyu, who is in charge of the State Flood Control and Drought Relief Headquarters, urged "the full implementation of all anti-flood ... measures so that human casualties and property loss can be reduced to a minimum," Xinhua said.