Heavy rain is forecast to drench Vietnam's northern mountains over the next four days due to a low pressure system and a tropical cyclone in the Gulf of Tonkin, the National Center for Hydro-Meteorological Forecasting said on Sunday.
Overnight downpours are expected to raise water levels in the Red River, where it flows through Yen Bai Province, to emergency status.
Local people have been warned of the possibility of landslides and flash floods in the region.
Earlier this month, floods in northern Vietnam killed 26 people and washed away hundreds of homes, causing damage estimated at more than VND940 billion ($41 million), according to the government.
The flooding crippled four provinces, damaging irrigation systems, fruit farms and rice fields.