The ferry overturned in a river in the south-eastern province of Fujian, causing the deaths of 11 people with four missing, web portal qq.com reported.
Nine people were killed in Dongguan, in Guangdong province in the south, according to the report. It showed images from the city of a car windscreen which appeared to have been smashed by egg-sized hailstones.
Many of the dead in Dongguan were trapped in collapsed buildings. Another 148 people were injured, including 11 who were critically ill, the report said.
The website put the death toll at 24, as did state-run news agency Xinhua.
Other provinces affected by storms and torrential rain on Wednesday were nearby Jiangxi, Hunan in central China and Guizhou in the southwest.
A total of 1.53 million residents have been affected by severe weather and 215,000 people were forced to relocate, Xinhua said, citing the Ministry of Civil Affairs.