Quang Ninh travel's climate is symbolic of the climate of North Vietnam; featuring all four seasons. In summer, it's hot, humid and rainy, while monsoons flourish. In winter, it's cold, dry, and sees little rainfall.
The average heat radiating during a year is 115.4 Kcal/sq. cm. The average temperature is over 21oC, while the average humidity is 84%. Annual rainfall totals between 1,700 and 2,400 mm, and there can be between 90 to 170 rainy days in a year. These are mainly concentrated in the summer (more than 85%), and especially in the months of July and August. In winter, rainfall only reaches between 150 and 400 mm.
In comparison to other provinces in the north, Quang Ninh has been more under the influences of north-eastern monsoons. The wind blows strongly and the temperature drops to between 1 and 3ºC. During a north-eastern monsoon, high mountainous regions such as Bình Liêu and Hải Hà, Ðầm Hà sometimes see the temperature drop below 0ºC.
Storms have a large influence on the province, mainly in June, July and August. The intensity can be extremely strong, especially in island and coastal regions.
Due to differences in terrain, the climate of sub-regions vary. The border area of the Mong Cai Tra Co District is colder and rainy, with an average temperature of around 22ºC and rainfall reaching 2,751 mm. In the Yên Hưng District, the most southern area, the average temperature is 24ºC and sees an average rainfall of 1,700 mm. The high mountainous region of Hoành Bồ, and Ba Chẽ districts, is victim to 20 days of frost a year, and is subject to little rainfall. In the Bình Liêu District there is heavy rain (2,400 mm) and winter lasts for six months. The offshore island region is not the wettest area, with only 1,700 to 1,800 mm of rainfall per year, but winter is often accompanied by thick mists.
The best time of year to visit Halong Bay is during the spring or fall. Because the bay is situated in the northern part of the country, it can get colder in the fall and winter, and though you won't see extremes such as blizzards, it's still a lousy place to be when it gets cold. This area is one of the most popular destinations for vacations in Vietnam. Though there will be more tourists in the area in the spring and summer, the area is still a good place to go.
In some situations, it's actually better that there are more people there. There will be more places to go for food and more entertainment in the area. When the weather is good you can go out in the bay on a junk, or a boat, and take a tour of the area. You can go swimming if you wish and just explore the beauty of the area. You can't do all of that in the fall and winter because it gets too cold. When you visit the area you should pack a swim suit, some shorts and a t-shirt. You should have enough clothes to keep you comfortable.