According to the National Centre for Hydro-Meteorological Forecasting, scattered showers and thunderstorms continued across the region on Sunday with some areas recording more than 40 mm of rain.
Northern localities and Thanh Hoa and Nghe An received 10-30 mm of rain, with isolated areas likely to record more than 100 mm.
The prolonged spell of heavy rain is expected to increase the risk of flash floods and landslides, particularly in mountainous and midland areas of the north.
Forecasters said the unsettled weather is likely to persist for several more days.
Elsewhere, most central provinces are expected to remain largely dry with sunny conditions and no widespread heatwaves.
Rain may ease temporarily across the Central Highlands and southern Vietnam on Monday before increasing again from August 4, with isolated heavy downpours expected in the afternoons and evenings.
