Quang Ninh is a mountainous and coastal province, with more than 80% of its area being made up of mountains and hills.
The sea and island zone of Quang Ninh has a unique terrain. There are more than 2,000 islands, making up two thirds of the Vietnam's islands. They extend along the coast for more than 250km and divide into numerous layers. The largest islands are Cai Bau and Ban Sen, while the smallest are just like rocks in a garden. The sea bottom terrain of Quang Ninh isn't smooth, and 20m-average depth. There are the remnants of ancient streams and underwater rocky banks. The streams from the mainland connect to deep drains along the sea-floor; creating a series of waterways, canals and harbors along the coast.
Climates:Quang Ninh's climate is symbolic of the climate in the North Vietnam; featuring all four seasons. In summer, it's hot, humid and rainy, while monsoons flourish. In winter, it's cold, dry, and sometime rainly.
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 2,400mm, 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 400mm.
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 Binh Lieu and Hai Ha, Dam Ha 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 Town is colder and rainy, with an average temperature of around 22ºC and rainfall reaching 2,751mm. In the Yen Hung District, the most southern area, the average temperature is 24ºC and sees an average rainfall of 1,700mm. The high mountainous region of Hoanh Bo, and Ba Che Districts, is victim to 20 days of frost a year, and is subject to little rainfall. In the Binh Lieu District there is heavy rain (2,400mm) and winter lasts for six months. The offshore island region is not the wettest area, with only 1,700 to 1,800mm³ of rainfall per year, but winter is often accompanied by thick mists.