Chinese forecasters have warned that the Yellow River, the nation's second longest, may suffer serious flooding as the south endures some of its worst storms and floods for decades.
Already reeling from a devastating earthquake, China has suffered floods across its south in recent days that have killed 57 people and forced 1.27 million to move to safer ground, according to the Ministry of Civil Affairs.
The National Meteorological Authority has also warned that the 5,500-km (3,400-mile) Yellow River flowing through the north may also see "quite large" floods this year due to unusually heavy rain in a catchment region, the official Xinhua news agency reported late on Sunday.
A fresh swathe of heavy rain likely in the next few days will "increase the destructiveness of flood hazards and make the flood prevention and relief situation nationwide even more serious", Xinhua cited the authority as warning. "The national flood prevention and relief effort is entering a crucial phase."
The Yellow River, China's second longest after the Yangtze, has experienced devastating floods in the past, but in recent decades has been more prone to water scarcity.
This year's floods have been especially heavy in Guangdong, the far southern province that is home to much of the country's export businesses. As of Sunday, 20 people in Guangdong had died in the floods and eight others were missing, provincial flood officials told Xinhua.
Forecasters have warned that in coming days, fresh storms could lash parts of the Yangtze River delta region near Shanghai, and provinces across the east, south and southwest.
Storms also recently brought havoc to Hong Kong, where they sparked flooding and landslides and resulted in closed roads and delayed flights.
The flooding and foul weather is the latest in a string of disasters to befall China this year.
The same provinces were also badly hit by freak cold weather and ice storms in January and February, and parts of the country's southwest province of Sichuan were devastated by a May 12 quake that killed more than 69,000 people.