According to Vietnam's meteorological agency, a tropical depression is currently active in the northwestern Pacific, about 2,500 kilometres east of the Philippines.
Forecasters expect the system to strengthen into a tropical storm within the next 24 hours before moving west-northwest toward Taiwan, China.
Around June 23-24, the storm is forecast to move into waters northeast of the Philippines. Its circulation could then influence weather conditions in the northeastern part of the northern East Sea.
The National Centre for Hydro-Meteorological Forecasting said the Red River Delta is expected to experience hot weather in the coming days, with some areas facing severe heat. Maximum temperatures are forecast at 35-36 degrees Celsius, with isolated locations exceeding 37 degrees Celsius.
From June 21, the heatwave is expected to expand into the northern midland region.
The agency also forecast continued hot and extremely hot conditions from Thanh Hoa Province to Danang, as well as in eastern areas stretching from Quang Ngai Province to Dak Lak Province.
Maximum temperatures in these regions are expected to range between 36 and 38 degrees Celsius, with some locations likely to exceed 38 degrees Celsius. The heatwave could persist for several more days.
Elsewhere, scattered showers and thunderstorms are forecast during the evening and night, while daytime conditions will remain generally sunny, with some areas experiencing hot weather. In southern Vietnam, scattered showers and thunderstorms are expected during the late afternoon and evening.
Between June 25 and June 28, northern Vietnam is forecast to see widespread rain and thunderstorms.
Around June 26-27, mountainous and midland areas in the north may experience a spell of moderate to heavy rainfall.
In the Central Highlands and southern Vietnam, thunderstorm activity is expected to increase from June 24 onward, with some areas likely to record heavy rain.