Vietnam is located in the monsoon zone. Weather is hot and humid from north to south (winter only exists in the north from November to April)
Undoubtedly, weather is one of the determining factors for your traveling decisions. If you are heading to Vietnam, then, take it easy to make up your mind. Vietnam’s climate is not just steamy hot as what you are frequently exposed to on movies. All year round here, there is always a perfect place where it is pleasant to stay. Basically, the whole country falls into the tropic and subtropics but its stretching length and diverse topography allow it to span several different climate zones. The weather thus, tends to vary considerably from season to season and also from region to region.
The North of Vietnam is generally cooler than other South East Asian regions in the same longitude. It experiences two main distinct seasons. In winter months, the weather gets colder and colder from November to March and considerably warmer in April (a leap into summer). This is also time to observe much cloud and frequent drizzle. The average winter temperature is 17.2°C (62.9°F). Particularly, the mountainous areas (Northwest) are often much colder, temperature may keep below 10°C (50°F) for long period. Ice and snow even cover Hoang Lien Son Mountains and nearby Sapa town for some times with the lowest record of -3°C (26.6°F) in Feb 2008.
In the summer (from May to October), the whole region is quite hot. Temperature may rise to 37°C (98.6 °F) in the peaks of June and July. Hanoi and coastal provinces around the Red River Delta generally enjoy equitable weather with high average humidity (80%) all year round though they may occasionally be subjected to typhoons and heavy rain in late summers (September to November). Vietnamese people even identify four seasons in the Northern provinces (from Hai Van Pass toward the north) with their distinct features: pleasant spring (typically March-April) and autumn (October-December), a chilly winter (December- February) and a hot summer (June – July).
The Central Vietnam with two sub-regions, coastal lowlands and central highlands, can be seen as an in-between climatic area of the North and the South. The coastal strip is usually dry and hotter than the rest in the summer, as the Truong Son Mountains do not allow it to enjoy most rainfall of south-western monsoon (from April to October). Unprotected coasts in their turn, however, make it wet and colder than the rest in winter-monsoon season (from November to March). Also, storms and typhoons strike this area more frequently than the northern coasts in summer months (from July to November). The Central Highlands in particular enjoys nearly double the average rainfall of the country. Two biggest towns in this plateau, Dalat and Pleiku, are ideally cool throughout the year. Near-the-south coastal cities, Quy Nhon, Nha Trang and Phan Thiet, on the contrary, experiences steamy hot weather (21°C-32°C / 70°F-90°F) all year round.
The South of Vietnam, merely 8 degrees north of the Equator, is typical of humid tropical climate which is excellent for growing rice. The region’s temperatures experience little variations in a year (around 27-32°C/80-90°F). There are two main seasons: the rainy and the dry. During the rainy/monsoon season (from May to November), downpours are expected to happen nearly every afternoon, resulting in occasional street flooding in and around Saigon. In the dry season, it is hot from late February to April then slightly cooler when first downpours come. Ho Chi Minh city (Saigon) enjoys rather equitable tropical climate with high humidity all year round. December to March is said to be the most pleasant time to hit this region’s center.
Note: In all, Vietnam climate is so diverse that there is almost no definition of an average temperature for the whole country. Thanks to these regional variations in weather, generally, you can drop in Vietnam at any time of year. Commonly, based on the duration of your stay, you should plan to catch the good weather and places by either dropping in Saigon in February or March then following the coast to north or hitting Hanoi in October-November then tracing southward. The choice is entirely yours.