Annual rainfall is between 2000mm and 2200mm. Ha Long bay has typical diurnal tide system (tide amplitude ranges from 3.5-4m). The salinity is from 31 to 34.5MT in dry season and lower in rainy season.
Best time to travel Halong
It is possible to visit Ha Long Bay year-round, with the best time to visit from October through April, although during the winter months of December, January and February, the weather in Halong Bay can be cool and overcast with low visibility. During the summer months from May to September, temperatures rise and storms are more likely during the rainy season.
12 moth weather
March April + May: Temperature: ~ 20°C-22°C; Some days have light rain; Clear with blue sky.
June + July + Aug: Temperature: ~ 26°C-28°C with strong Sun; Carefully with Typhoon; Some days have trong but quick rain.
Sept + Oct + Nov: Best time to enjoy Halong with cool temperature: ~ 26°C-28°C.
Dec + Jan + Feb: Temperature: 18°C~20°C; Cold with strong wind; Some days are misty and rainy.