According to the National Centre for Hydro-Meteorological Forecasting, scattered thunderstorms and locally heavy rain of more than 70mm are forecast for the northwestern and northern mountainous regions from the evening of May 12.
Authorities warned residents to prepare for dangerous weather conditions during thunderstorms, including whirlwinds, lightning, hail and strong winds.
The agency said the extreme weather could disrupt agricultural production, uproot trees and damage homes, transport infrastructure and public works.
Localised heavy rain may also trigger flash floods on small rivers and streams, landslides on steep slopes and flooding in low-lying areas.
Forecasters expect a broad heatwave to develop across northern Vietnam and the north-central region from May 13, with particularly severe heat in western mountainous provinces.
US-based weather service AccuWeather forecast that Hanoi would experience hot weather on May 12, with temperatures reaching 33 degrees Celsius.
