Vietnam has a subtropical climate, during the months of December, January and February it is their equivalent to winter and this is the coolest time of the year. In southern and central Vietnam, the days can still be warm but the evenings cooler and dryer, making this one of the best times to visit this region. Northern Vietnam, especially in the mountainous areas such as Sapa, can get quite cold and experience light rains at this time of year and you will need a pullover or jacket. It can snow at this time in Sapa and surrounding areas. There are occasional storms in Central Vietnam
During the months of April and May it is their equivalent to spring and September and October being autumn. These four months enjoy almost identical weather conditions, with usually mild and warm weather.
During the months of March and November Vietnam enjoys warm temperatures, with March being early spring and November being late autumn. These two months enjoy almost identical weather conditions with mild and less humid weather. However, in November, central Vietnam experiences occasional storms and the weather begins to get colder. You will need a pullover or jacket in mountainous areas like Sapa
During June, July and August it is the wet season for most parts of Vietnam; their equivalent to summer, experiencing warm temperatures and humidity, which is relieved by the monsoonal rains that take place most afternoons.