Halong bay has a humid tropical climate. There are however four seasons in the North. Winter lasts from December to March; temperatures can drop down to 12°C-17°C. Summer is from May until September, mostly sunny but rain showers are frequent as the humidity is higher. Spring and Autumn are nicely warm, October to early December being the best time to visit the area. Travellers to Vietnam and Halong Bay should be aware that the weather is rather unpredictable and can vary greatly even within one single day. However, there is charm and enchantment whether rain or shine: overcast weather and fog make the scenery more mysical and dramatic, bright sun accentuates the various shades of grey of the seascape, etc.