The capital, Hanoi, is a little further to the south and about 90 km (55 mi) from the sea. Winter averages are a little higher, however, sometimes there can be very cool periods here as well, with lows around 7/8 °C (45/46 °F) and highs around 15 °C (59 °F); more rarely, it can even get cold for a few days, and highs can drop to around 10 °C (50 °F). Here are the average temperatures.
December – March: cool to cold, misty, cloudy
April – June: warm to hot, clear skies, sunny
June – August: hot, humid, rainy
September – November: cool, clear skies, sunny
The winter monsoon is originally dry because it comes from the Asian continent, but the clash with the mild and moist air of the Gulf of Tonkin generates compact cloudiness, which bring light but frequent rains. Therefore, during winter, the sun rarely shines in Hanoi, and although the temperature is spring-like, a journey to this city would not be so pleasant. Hanoi is actually a dull city, in fact, even in summer, the sun does not shine very often because of the summer monsoon. There are about 1,450 hours of sunshine per year. Here are the sunshine hours per day in Hanoi.
In spring, the temperature gradually rises in northern Vietnam, and the sun comes out every so often in April, but then, from May to October, it’s the rainy season, and the weather becomes hot and humid, with downpours in the afternoon or evening. In Hanoi, the wettest months are July and August, with about 300 mm (12 in) of rain per month. The maximum temperature is around 33 °C (91 °F), but the humidity makes the heat annoying, also because it can sometimes reach as high as 37/38 °C (99/100 °F), with peaks of 39/40 °C (102/104 °F) in May and June.
In October and November, when the monsoon withdraws, there is another quite pleasant period, before the return of cool and dull weather in December.
Here is the average precipitation in Hanoi.
The best time to visit Hanoi is usually from April to June or from September to December. From April the days are normally hot, occasionally above 30 degrees with clear skies. September to November sees cooler temperatures of around 25 degrees and sunny skies — perfect for exploring the capital.
If you’re coming to Hanoi in June, expect soaring temperatures with humidity highs of 40 degrees, and the rainy season is full swing (June to August). December is cool, misty and atmospheric, however from late December until March temperatures are surprisingly cold with lows of 10 degrees. You’ll want to bundle up.
Read more: Best Time To Visit Vietnam