Climatic complications
Although the weather in Vietnam is extremely variable, it’s possible to distinguish two main seasons: a dry season from November to May, and rainy season from June to October. However, this generalisation disguises considerable variations in other aspects of the weather throughout Vietnam. For example, in the south of Vietnam the difference in temperature between two seasons is a hardly noticeable 3°C with little variation. In the north, the difference averages 12°C but can vary from under 10°C in winter to a summer extreme near 40°C.

The summer months: from April to October.
The winds of the south-western monsoon blow across the country. Laden with moisture from the Indian Ocean and the Gulf of Thailand, they bring warm, humid weather to most of the country with the exception of those areas sheltered by mountains, such as the central coastal lowlands from about Nha Trang to Nghe An.

Apart from the Central Highlands and mountain areas, temperatures are uniformly hot across the country during the summer months, and humidity is high.

The winter months: from November to March.
The winter monsoon comes from the northeast. The winds that blow upon the central coastal area during November and December have crossed the Pacific and bring heavy rain, often causing severe flooding, technically known as a Thailandian monsoon climate.

The north and the Red River Delta are sheltered by the landmass of China, but experience cold, clammy weather that can last from December to April, but mainly occurs during February and March. In the northern mountain areas, temperatures are generally cooler in both summer and winter. Occasionally, the area around Mt. Fan Si Pan experiences winter snowfalls.

The Central Area
The Central Area has two distinct sections: a long coastal lowland strip facing the Eastern Sea, and, further inland, an equally long highland plateau to the west. This creates an unusually diverse pattern of weather.

From April to October, the south-western monsoon deposits its rain on the Truong Son Mountains. As a result, the beaches and resorts of the coastal strip enjoy warm, dry weather along nearly all year round.

Heavy rain falls during October and November along the southern section of the central coast. In autumn, nearly all the central coast experiences intermittent, strong on-shore winds. These can generate powerful waves and an undertow making swimming off some beaches risky at times.

Temperatures in the Central Highlands are generally cooler all year round, but hot weather and prolonged droughts sometimes occur early in the year.