Five dead were found in a factory building that collapsed in Fujian province in the southeast and another three in the landslides of a residential building, according to the state-run New China news agency.
Another five people died and three are missing in the southwestern province of Yunnan, state CCTV reports.
Three children were swept away by floods in the Guangxi region.
Two of the children died.
The torrential rain began on Thursday evening, local time, and the water masses have destroyed crops, caused power outages and destroyed nearly 40 houses in the area.
More than 1,600 people have had to be evacuated.