The worst-hit was Inner Mongolia where at least eight people were killed in torrential rains and hail in Erdos City, Xinhua News Agency reported. The report said several homes in the district remained flooded.
Flooding was blamed in the deaths of four people in eastern China's Anhui province. Another four people remained buried in the rubble of collapsed homes in the province, the news agency said.
Two other people died in flooding and landslides in southwestern Sichuan province, Xinhua said. At least five more people remained missing in the province and search efforts were under way to find them.
Heavy rains were forecast to continue through Tuesday in some of the affected regions as well as in northern and northeastern China.
Forecaster also said Rumbia, the sixth tropical storm to hit China this year, was expected to head toward Guangdong and Hainan provinces after entering the South China Sea.