Temperatures in southern Vietnamese localities are forecast to exceed 35 degrees Celsius and reach 37 degrees Celsius from Thursday to next Monday, according to the Southern Center for Hydro-Meteorological Forecasting.
The heatwave will peak from Thursday to Sunday.
Amid the higher temparatures, the ultraviolet (UV) index will reach extremely harmful levels in the next three days in both central and southern Vietnamese localities, including Ho Chi Minh City.
In Da Lat City in the Central Highlands province of Lam Dong, the UV index will be as high as 11, the most extreme reading in the scale.
High UV levels can damage human skin and eyes within minutes, according to the World Health Organization.
The Mekong Delta and the southeastern regions will continue to experience scorching weather and little rainfall over the coming days.
From Thursday to Sunday, the salinity level will increase in the Vam Co River system and Mekong estuaries, then decrease gradually.
Meanwhile, saline intrusion is likely to exacerbate in the Cai Lon River from March 16 to March 20.
The National Center for Hydro-Meteorological Forecasting advises people in the Mekong Delta region to limit watering their crops in order to minimize production damage between Thursday and March 16.
In areas where fruit with low salt tolerance is grown, farmers should check salinity levels before irrigation.