On Sunday, northern Vietnam was affected by low-pressure air circulation carrying heat from the west, cranking up temperatures in Hanoi at around 1 p.m. to 36 degrees Celsius, while mountainous areas like Son La saw temperatures at around 37 degrees Celsius.

Locations of over 1,500 meters above sea level, like Sa Pa in Lao Cai meanwhile experienced temperatures of up to 24 degrees Celsius, according to the National Center for Hydro-Meteorological Forecasting.

On Sunday, the low-pressure circulation is expected to work in concert with the Foehn wind to expand the heat zone to northwestern regions. Temperatures are expected to be within a 35-37 degrees Celsius range for northern Vietnam until the end of the week, the center said.

U.S. forecast service provider AccuWeather said temperatures ranged between 27-36 degrees Celsius in Hanoi on Monday, and could rise up to 37 degrees Celsius by the weekend. For high-altitude areas like Sa Pa, temperatures would range between 17-25 degrees Celsius.

In central Vietnam, sunny days and a heated atmosphere should also be expected in cities and provinces from Thanh Hoa to Quang Ngai, with temperatures reaching up to 39 degrees Celsius.

Across southern Vietnam and Central Highlands regions, the heat is expected to affect southeastern parts, with temperatures reaching up to 37 degrees Celsius. Sunny days should be expected in the region until May 13, after which rains should return to lower temperatures.

Northern Vietnam should experience its hottest period from the end of May to July, and central Vietnam from the end of June to August. But overall, the heat would not be as intense and long-lasting as it was last year, the center stated.