Hanoi features a warm humid subtropical climate with plentiful precipitation. The city experiences the typical climate of northern Vietnam, where summers are hot and humid, and winters are, by national standards, relatively cool and dry. Summers, lasting from May to September, are hot and humid, receiving the majority of the annual 1,680 millimetres (66.1 in) of rainfall. The winters are short, relatively dry, and mild, while spring can bring light rains.
If you are thinking you have a fairly good idea about the weather in Vietnam and Hanoi will be a similar case, then, you are wrong. The climate of Vietnam varies greatly from north to south due to its long and narrow territory and you can never judge Hanoi's weather from the knowledge of other Vietnamese regions.
Hanoi area, lying in a plain, belongs to the delta region of Red river and far form sea, it features of hot climatic zone under the influence of South and Northeast monsoons.
Hanoi experiences the typical climate of northern Vietnam where summers are hot and humid and winters are relatively cool and dry.
Summer months remain from May to September and the months are characterized by extreme hot weather with plenty of rain.
Summer in Hanoi can get as hot as 38°c to 40°c (100-104°F).
June can be labeled as the most sweltering hot month of the year with mercury rising up to 33°c to 39°c.Winter rules from November to March. The weather remains cold and dry.
The minimum winter temperature in Hanoi can dip as low as 6-7°C (43°F)
Northeast monsoon are frequent during the winter months.
January is the coolest month usually accompanied by a cold north-easterly wind. The lowest temperature in average is 12°c.
So, the annual temperature varies from 8°c to 38°c.
During the transition months of April and October, the weather becomes unpredictable as you should be prepared for anything.
Typical of a humid tropical climate, Hanoi is characterized by monsoons like most of northern Vietnam.
The time from July to September witnesses heavy rainfall and sometimes, the excessive rainfall leads to floods.
Autumn and first haft of winter is the most beautiful season in Hanoi.
Best time to visit Hanoi
Hanoi is most pleasant from February to April and September to November avoiding the heat and the rain. The official peak season in Vietnam is from September to April.