Throughout last week a low-pressure area in the west brought sweltering heat to the region. On Sunday Hanoi recorded a maximum of 38 degrees Celsius (100.4 degrees Fahrenheit), according to the National Center for Hydro-Meteorological Forecasting.

But relief is on hand due to a trough combined with wind convergence in high altitudes, which would bring rains, it said.

Temperatures in Hanoi would be a milder 27-34 degrees on Monday before gradually rising to 32 degrees on Thursday and 34 degrees by weekend, according to U.S. weather forecast service AccuWeather.

Places situated at altitudes of 1,500 meters or more like Sa Pa in Lao Cai Province would have temperatures of 17-24 degrees, it said.

The center said mountainous areas would have rains of 100-200 mm each time, with some areas getting over 250 mm. Flash floods, erosion and local inundation are possible in certain areas, it warned.

Lao Cai's downtown area already suffered flooding of up to one meter on many streets Monday morning following heavy rains the previous night.

There could be floods of one to two meters in the upstream portions of small rivers from July 5 to 7 due to the rains, the center said.

The central region will start cooling down on Tuesday, it said.