A tropical convergence zone over the north-central region is bringing prolonged heavy rain to the area.
From Thanh Hoa to northern Quang Tri, rainfall of 30-60 mm is forecast on August 31, with some areas receiving more than 130 mm.
From the evening of August 31 through September 1, southern Quang Tri to northern Danang is expected to receive 40-70 mm, with isolated totals exceeding 150 mm.
Forecasters warned that rainfall could exceed 100 mm in three hours in some places, raising the risk of localised flooding. Thunderstorms may also bring tornadoes, lightning, hail and strong gusts.
In the north, scattered rain is forecast mainly in coastal Quang Ninh, Haiphong, Hung Yen and Ninh Binh, while elsewhere will see little rain and intermittent sunshine.
Hanoi will have intermittent sunshine and little rain, with temperatures ranging from 26-28 degrees Celcius to highs of 32-34 degrees Celcius.
The Central Highlands will see little rain in the morning, followed by scattered showers and thunderstorms in the afternoon and evening, with isolated heavy rain. Temperatures will range from 20-23 degrees Celcius to 26-29 degrees Celcius.
Southern Vietnam will see intermittent sunshine and little rain during the day, with scattered showers and thunderstorms developing in the late afternoon and evening. Temperatures will range from 24-27 degrees Celcius to 30-33 degrees Celcius.
HCM City will see similar conditions, with scattered showers and thunderstorms later in the day and temperatures of 24-34 degrees Celcius.
Rainfall of 15-30 mm is forecast across the Central Highlands and southern Vietnam on August 31, with isolated totals above 70 mm. Scattered evening and overnight thunderstorms are expected to continue in the coming days, with locally moderate to heavy rain.