The north of the country lies in the subtropics, whereas the south is under the influence of the tropical climate zone. While in the northernmost mountains you may encounter frosty winters; on the other hand, you can expect equatorial climate around the delta of the Mekong river. The average temperature in the south is around 27 °C. In contrast, the north offers 21 °C at most. The geographical altitude plays an important part as well; it is not uncommon that when temperatures are as low as 0 °C in the northern mountains, in the south they approach 40 °C. Monsoons also exert a strong influence: the northern monsoon controls the weather from October until March. In the north of the country it manifests itself as a cold and humid winter, but it is quite warm in the south at the same time of the year. The tropical south only has two seasons: the wet season (from May to November, the rainiest months being June, July, and August) and the dry season (from December to April). The air is usually the hottest and most stuffy from the end of February until May.
The main tourist season: January – May, October – December.