China's national observatory renewed a blue alert, the lowest in a four-tier warning system, on Sunday for rainstorms.
From Sunday to Monday, heavy rain is expected in southern Zhejiang, southeastern coastal regions, Guangdong and Taiwan, the National Meteorological Centre (NMC) announced.
Some areas will see torrential rain accompanied by thunder or hail, according to the NMC.
The NMC had issued a blue alert for rain on Saturday before this renewal, Xinhua news agency reported.
Local authorities were asked to prepare for emergencies, halt outdoor work and prevent floods and landslides.
China has a four-tier colour-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.