Because of the terrain differences, the climates of sub-regions differ. The border area of the Móng Cái District is colder and rainy, with an average temperature of around 22 °C and rainfall reaching 2,751 mm. In the Yên Hưng District, the most southern area, the average temperature is 24 °C and gets an average rainfall of 1,700 mm. The high mountainous region of Hoành Bồ, and Ba Chẽ districts, has 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.