Vietnam is a very long country stretching from North to South over 2000 kilometers. The weather varies along the year and the region.
Monsoon lasts from the end of June to the end of August with very high temperatures (35-40 degrees) and levels of humidity close to 100%. Huge rain drops, often in the late afternoon but not every day. It is ok to travel during this time of the year, but avoid planning too much physical activity and avoid places too much remote in the mountains of the far North (rain sometimes occasions landslides that destroy roads). Phu Quoc Island, which offers beautiful conditions the rest of the year, might be quite rainy during these months.
From September to June, the weather in South Vietnam is quite stable. It is never cold and always dry. Mekong Delta, Saigon, Dalat, Mui Ne… go easy and dress light.
In the North, autumn (September to the end of December) and spring (April to mid-June) are the best times to travel weather-wise. Temperatures are hot but not too much, humidity levels are relatively low, rains are pretty rare. September/October and May/June are the two best periods to admire terraced rice fields. 50 nuances of green and plenty of related farming activities. January and February can be pretty cold and even freezing in the mountains. March is almost drizzling 24/7. These 3 months are the worst to travel the Northern region. Plus it is Têt festival (Lunar New Year) and booking some services can get complicated.
Central Vietnam is hit by a typhoon season from late October to February. However, typhoons are quite seldom and impossible to predict long in advance. So no restriction for Central Vietnam. Plan to have a windstopper or light jacket in your bag to prevent cooler mornings and evenings from December to February.
So the few points to note:
- Best season for the whole country: September/October and May/June.
- Winter can be freezing in the North. Do not rely on air temperature; real feel due to humidity is the key.
- Phu Quoc Islands has its worst weather of the year in July and August.
- Rice fields of the North are empty from late October to April.
- November/December and March/April are the peak seasons for tourism. Better book long enough in advance.