According to the Southern Hydro-Meteorological Center, a tropical low pressure has been forming in the waters off the Philippines and is able to enter the north region of the South China Sea, known as the East Sea in Vietnam, strengthening the southwest monsoon wind.

This would result in rain falling across multiple areas, including southern regions. HCMC and southern provinces are forecast to enter monsoon season with first rains on a large scale this Friday.

Le Dinh Quyet, meteorologist of the center, said more downpours in HCMC are expected to last until the end of this month with heavy rainfall of up to 100 millimeters, which could cause flooding in some districts of the city.

Heavy downpours followed by serious flooding are the norm in Ho Chi Minh City during the rainy season, which lasts from May till the end of October each year.

The arrival of long-expected rains could help reduce Saigon temperatures by up to 10 degrees Celsius from the 37-38 degrees Celsius of the past sweltering weeks, Quyet said.

Amid a severe heat wave, consistently high UV levels have been threatening Vietnam's largest city, with the index jumping to 'dangerous level' on many occasions during the month.

Data from Weather Online, a U.K.-based meteorological services provider, indicate the index in HCMC would climb to a 'very high' level of 11 from Tuesday to Thursday, posing health risks to holiday-goers engaged in outdoor activities.

The UV Index would reach 9 this Friday as rain is expected to appear to placate the scorching heat.

The UV Index is an international standard measurement of the strength of ultraviolet radiation from the sun. Between 0 and 3 is considered low and above 11 is deemed extreme with radiation that could burn skin and damage eyes within 20-30 minutes.

American forecast services provider AccuWeather said the city's UV would reach 12 Wednesday and 11 Thursday. It also forecast there would be rains and thunderstorms in some parts of HCMC on Friday night.

It estimated the city's temperature for the rest of the month to be around 33-34 degrees Celsius.

During last year's summer, Vietnam already saw average temperatures climbing 0.5-1 degrees Celsius from previous years, to 39-42 degrees Celsius in many parts of the country. On April 20, the mercury hit the record 43.4 degrees Celsius, or 110 degrees Fahrenheit, in Huong Khe District, Ha Tinh Province in central Vietnam.