Climate in Ha Long (Vietnam)

In Ha Long, there is a subtropical climate, with very mild winters and hot, humid and rainy summers. The sun shines quite rarely. The rainiest period is from May to October, due to the monsoon of Southeast Asia.
Ha Long (or Halong) is located in northern Vietnam, in the province of Quảng Ninh, at 21 degrees north latitude, on the coast of the Gulf of Tonkin. To the north are mountains about 900 meters (2,950 feet) high.
Ha Long Bay is located near the coast and is home to several islands and islets, and is itself divided into two parts. In the west we find Lan Ha Bay, with the Bay islands, which are protected in a national park. The main island is Cat Ba. Further east we find the islands of Bai Tu Long Bay, whose main island is Tra Ban.
Further from the coast is the island of Bạch Long Vĩ.

The winter, from December to February, is mild, however, the sky is often cloudy, especially in January and February, and drizzle can occur.
Winter averages are a little higher than in the far north of Vietnam, 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).
The summer, from May to September, is hot and muggy, with frequent and sometimes heavy rains. During the pauses between a period of bad weather and the next, it can get very hot, and the temperature can reach 37/38 °C (99/100 °F).
Here are the average temperatures.

On average, about 1,900 mm (75 in) of rain fall per year, of which more than 150 mm (6 in) per month fall from May to October. Although precipitation in winter is weak, as mentioned, especially from January onwards, there are frequent drizzles.
Here is the average precipitation.

Ha Long is a dull city, although the sun shines a little more often than in Hanoi. In any case, it is rarely seen from January to April, but even in summer, it does not shine very often because of the summer monsoon. There are about 1,700 hours of sunshine per year. Here is the daily average.

In Ha Long, the sea is a bit cool from January to March, while it is very warm in the summer months. Anyway, in winter, cool and cloudy weather conditions which prevail in this season are usually not inviting for swimming.

The city can be hit by typhoons, the tropical cyclones of Southeast Asia, and it should be remembered that the coast is the area most at risk. Typically, typhoons pass in this area from late May to early November, with a maximum from July to October.

Best Time

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In Ha Long, there is no time of year when the temperatures are mild, the sun shines and there is little rain. However, you can choose spring and autumn, and in particular, from mid-March to mid-April and from the end of October to the end of November.
In winter, December is a little sunnier and less cool than January and February.