In worst-hit Guangxi region, 300 students have been trapped inside their school since Saturday by the high flood waters.
Flood control officials have used boats to deliver food, mineral water and other supplies.
The heavy downpours also inundated crops and cut power across several provinces.
Last week China's national flood prevention office estimated that the floods had caused losses of more than $1.58bn.
Since then the floods have spread, likely pushing up the costs to families and businesses.
Forecasters say worse weather may be on the way as the peak of the annual wet season nears.