The National Centre for Hydro-Meteorological Forecasting said northern provinces and cities, except Lai Chau and Dien Bien, as well as areas from Thanh Hoa to Danang and from eastern Quang Ngai to Gia Lai, would experience hot and locally severe heat.
Temperatures are forecast to reach 35-37 degrees Celsius in most areas, with some places exceeding 38 degree Celsius.
The hottest conditions are expected mainly between 11 am and 5 pm.
After August 12, hot weather is forecast to continue across most of northern Vietnam, except Lai Chau, Dien Bien, Quang Ninh and Haiphong.
In central Vietnam, the heat is expected to persist for several days.
Meteorological authorities have warned that high temperatures combined with falling humidity could increase the risk of fires and explosions in residential areas, particularly as demand for electricity rises.
People working or travelling outdoors for extended periods are also at risk of dehydration and exhaustion from prolonged exposure to high temperatures.
Temperatures reported in weather bulletins are measured under standard conditions. Actual outdoor temperatures can feel 1-3 degrees Celsius higher, and the difference can be significantly greater in areas with extensive concrete and asphalt surfaces or limited vegetation.