The front is also set to move on to the central region, according to the National Center for Meteorological and Hydrological Forecasting.

The cold front is quite strong, and with the winter wind bringing in humidity from the sea, a drizzle is also possible. Temperatures are likely to drop to 7-12 degrees Celsius.

The center says that on Tuesday, the cold front will lower temperatures in the north to 11-14 degrees Celsius, with the mercury dropping below 5 degrees Celsius in the mountains. It will be cloudy during the day and the difference in day-night temperatures is likely to be just 2-4 degrees Celsius.

According to the U.S. weather forecasts site Accuweather, on Monday noon, the temperature in Hanoi will still be at 21 degrees Celsius, but it will drop to 13 at night.

From December 15-17, the temperature in Hanoi will fall further to around 12-14 degrees Celsius before increasing by 1-2 degrees every day.

In mountainous areas 1,500 meters above sea level, like Sa Pa in Lao Cai Province, the mercury will drop to 9-15 degrees Celcius with small rain likely from December 15 to 18.

Nguyen Van Huong, Head of the Weather Forecasting Department at the center, said that this will be the first large-scale cold wave in the north during the 2020-2021 winter season.

The areas most affected are likely to be the provinces of Cao Bang, Bac Kan, Lang Son, Ha Giang, Tuyen Quang and Lao Cai. The front can last three to five days.

With low temperatures and drizzles in some places, it is possible that Mount Fansipan in Lao Cai and the peaks of Mau Son (Lang Son), Sin Ho (Lai Chau) and Phia Oac (Cao Bang) will experience frost.

The strong cold front will then proceed to central Vietnam on December 15, causing rain in provinces from Thanh Hoa to Binh Thuan. On December 15-16, the area from Ha Tinh to Quang Ngai is likely to receive heavy rainfall of 50-100 mm in 24 hours. The temperature in Vinh, the capital of Nghe An, will drop to 16-19 degrees Celsius, in Hue to 18-19 degrees Celsius and in Da Nang to around 20-24 degrees Celsius.

The weather is likely to remain mostly sunny next week in the Central Highlands and the southern region. On December 15-16, the southwestern region is likely see some unseasonal rain. The highest temperature during the day in the Central Highlands is estimated at 29 degrees Celsius. In the south, it is set to be hotter, at 33 degrees Celsius.

Due to the impact of La Nina, a coupled ocean-atmosphere phenomenon, the winter of 2020-2021 has arrived early, from mid-October onwards, accompanied by many storms, causing floods in the central region that left 249 people dead, 57 missing, more than 1,500 houses collapsed and nearly 240,000 others damaged.

There is a possibility of one or two tropical cyclones operating in the middle and the southern part of the East Sea this month, affecting the weather in the central and southern provinces, the national weather center said.