Tran Quang Nang of the National Center for Hydro-Meteorological Forecasting said that the northeast monsoon should arrive Oct. 10-11.

He said there will be two to three waves of cold air this month with average daytime temperatures in the northern region to fall below 25 degrees Celsius.

"This winter will be colder than last year and the northern region will face more cold snaps before Dec. 25," he said.

The peak of winter weather is set to arrive in January 2022, accompanied by four to five strong cold air waves causing severe cold for four to six days, he added.

The center said it is likely to rain in the north starting Monday and intensify from Tuesday due to the influence of strong easterly winds that will bring showers and stormy weather. In the coastal areas of the southern provinces of the northern delta, heavy rain is likely to occur until the end of October 7, the center said.

There will be heavy rain in the northern and central provinces October 5-7 and temperature in the central provinces will fall below 34 degrees Celsius

There will also be thunderstorms in the south and Central Highlands this week, concentrated in the afternoon and evening. The highest daytime temperature will be 28-30 degrees Celsius in the Central Highlands and 31-33 degrees Celsius in the southern region.

A tropical depression will enter the East Sea in the middle of the week, the center said.

On Sunday morning, a low air pressure formed in the southeast of the Philippines. Around October 6-7, this pressure will enter the East Sea, strengthen into a tropical depression, and could strengthen into a storm in the following days.

Nang said October and November are peak months of the rainy season in 2021 with many tropical depressions and storms forming in the East Sea.

He said the central provinces will have more frequent rainfall, 15-30 percent higher than the average of previous years.

Five to seven storms and tropical depressions are likely to form in the East Sea from now until the end of this year, with two to four storms directly affecting the Vietnamese mainland.