Hanoi’s climate is quite typical for the northern climate type characterized as tropical monsoon, with hot summers, heavy rain and cold winter, dry.
Hanoi is situated in a tropical monsoon zone with two main seasons. During the dry season, which lasts from October to April, it is cold and there is very little rainfall, except from January to March, when the weather is still cold but there is some light rain.
The wet season, from May to September, is hot with heavy rains and storms. The average annual temperature is 23.2ºC (73.7ºF) and the average annual rainfall is 1,800mm. The average temperature in winter is 17.2ºC (62.9ºF), but can go down to 8ºC (46.4ºF). The average temperature in summer is 29.2ºC (84.6ºF), but can reach up to 39ºC (102.2ºF).
Hanoi enjoys four distinctive seasons- spring, summer, autumn and winter.
The spring season is from February to April and is characterized by light drizzles keeping the weather wet. The season also culminates with the Lunar New Year Holiday and local folk festivals. The summer season is comparatively hot and humid and consists of the months of May to August. Temperatures can soar as high as 38- 40 degree Celsius. This season also registers the highest amount of annual rainfall which is around 1682 mm/ year. September to November is the autumn months. The weather is dry but cool and is considered to be the best season in Hanoi, however the duration is short. Winter lasts from December to January and are cold and dry with temperatures falling as low as 6-7 degree Celsius.