Relentless rains and floods have killed at least 41 people in central Vietnam since the weekend, while a search continues for nine still missing, state media reported.
The deluge has submerged more than 52,000 homes and left half a million households and businesses without power, according to reports.
Rainfall exceeded 1.5m (5ft) in several areas over the past three days, even rising beyond the 1993 flood peak of 5.2m in some parts.
The worst-hit areas include the coastal cities of Hoi An and Nha Trang, as well as a key coffee production belt in the central highlands - where farmers are already reeling from a stalled harvest because of earlier storms.
Extreme weather has battered Vietnam in recent months. Two typhoons, Kalmaegi and Bualoi, left a trail of deaths and destruction within weeks of each other.
Natural disasters in Vietnam have wreaked damage amounting to $2bn between January to October this year, according to government estimates.
Tens of thousands of residents have been evacuated across the flood-affected regions. Military troops and police officers have been deployed to set up emergency shelters to relocate people to safety.
Authorities have warned of moderate to heavy downpours in central Vietnam through Sunday at least.
