Halong weather is typical for tropical coastal climate, which has two main seasons all year around. From April to September, it is often hot and humid; from October to March the weather is dry with some cold months.
The average temperature of Halong Bay is 24°C. In the summer, the average temperature is 35°C while the maximum temperature recorded is 38°C. The heat may be reduced thanks to its location amid the mountains and grottos. On the other hand, during winter, it might get as low as 14°C in average, and the lowest could be as low as 5°C.
The city has a relatively high average annual rainfall, which is unevenly distributed depending on the two main seasons. During the rain season, and also summer, from May to end of August, the rainfall amounts for 80-85% of the total rainfall of the year, with the maximum in July and August. Winter, and also dry season (from November to April of the next year) witnesses little raining of around 15-20% of the total rainfall, with the minimum in December and January.
Halong is one of the most humid cities in Vietnam with the average annual humidity at 84%.
Thanks to the nature of a closed-sea area, Halong is lucky not to be much affected by heavy storms. The strongest storms on the bay normally are at level 9 and 10, hardly anytime reaching level 11.
Overall, Halong Bay is a year-round tourist attraction. It depends on your preference to decide the best month to visit Halong Bay. However, each month will bring you a whole new and different experience.
January:
January in Halong Bay is often cold and dry. It may not be best for swimming but definitely great for taking photos of the scenic landscape.
Being in the middle of the winter, January in Halong Bay is still rather cold with the average temperature at 17°C. The maximum temperature is only 20°C and the minimum temperature is around 14°C. While there is a long 11 hours of daylight, the sun is on for shining for only 3 hours everyday.
With the sea temperature of 21°C, it is not that cold to swim but it’s not recommended to swim in January. Bringing a sweater and a coat is a good idea to shield from the cold and occasional light rain and distributes over 10 days in Halong.
- Average temperature: 17°C
- Average sea temperature: 21°C
- Monthly rainfall: 18mm
- Average hours of sunshine per day: 3
February:
The average temperature in February is higher in January, making it a more comfortable time to travel to Halong Bay.
Being the last month in the winter, the average temperature in February in Halong is slightly higher at 18°C. This is because the lowest temperature at night increases to 15°C. However the number of sunshine for the month decreases to only 2 hours/day compared with January. The amount of rainfall increases, to average of 10 wet days. This starts to indicate the gradual change to spring in March before entering spring season. The sea temperature sustains at 21°C.
- Average temperature: 17.5°C
- Average sea Temperature: 21°C
- Monthly rainfall: 39mm
- Average hours of sunshine per day: 2
March:
March sees subtle changes in season from cold winter to humid spring. It is a good time to visit Halong Bay nevertheless.
With the first 2 weeks of March is still carrying the leftover winter chill, the later half of the month is seemingly warmer, signifies the start of spring in Halong Bay. The maximum temperature in March increases to 22°C and the minimum temperature at night time is at 17°C. With warmer temperature, the number of wet days in Halong bay during this month increases to 13 days. The length of daylight increases to 12 hours/day and the hour of sunshine increases to 3 hours per day. The average sea temperature slowly rises to 22°C.
- Average temperature: 19.5°C
- Average sea Temperature: 22°C
- Monthly rainfall: 43mm
- Average hours of sunshine per day: 3
April:
April is a good month to visit Halong Bay as there are few risks of storm and the weather is very accommodating for an outdoors trip.
This month marks the start of the ideal time to visit Halong bay. April has a maximum temperature of 26°C and the minimum temperature of 20°C. The number of sunlight during the day increases to 4 hours. The day light times starts to lengthen to 13 hours/day. It is also worth noting that the amount of the rainfall has increased. This increases in temperature and rainfall makes the heat and humidity discomfort level increases though it is still reasonably comfortable. The sea temperature is warmer, good for swimming at 24°C.
- Average temperature: 23°C
- Average sea Temperature: 24°C
- Monthly rainfall: 79mm
- Average hours of sunshine per day: 4
May:
May marks the start of a hot summer although the heat in this month is by and large endurable. It is in fact one of the best months to visit Halong.
Summer officially starts in Halong bay in May with the average temperature of 27.5°C. Night time temperature is at 24°C while the maximum day time temperature can spike to 31°C. The day is filled with sunshine for 6 hours and the daylight time can last for 13 hours. 14 days of rain makes the level of humidity and discomfort on land increases. This makes diving into the sea water of 27°C tempting. Bringing flip flops, shorts, tank tops and most importantly sunscreen is recommended.
- Average temperature: 27.5°C
- Average sea Temperature: 27°C
- Monthly rainfall: 192mm
- Average hours of sunshine per day: 6
June:
June is a rather hot month for travel to Halong Bay although it is perfect who loves the sun.
Compared to May, the temperature in June starts to rise but not too drastically. There is an increase in average temperature to 29°C. The length of daylight hours remain at 13 hours as well as the length of sunshine at 6 hours. However, half of the month is wet with total rainfall amounts is still increasing. This makes the weather very uncomfortable with high humidity level. The sea water temperature is similar to on land temperature of 29°C.
- Average temperature: 29°C
- Average sea temperature: 29°C
- Monthly rainfall: 277mm
- Average hours of sunshine per day: 6
July:
July is one of the rainiest month in Halong Bay. However, you will benefit greatly from the many promotions for cruise trips here.
July marks the start of the rain season in Halong with a spike in rainfall nearly doubles its amount. This is distributed in 15 days in the month. The maximum and minimum temperature, as well as the average temperature, remains roughly the same as June at 32°C, 26°C, 29°C respectively. 7 hours of blazing sun is expected during the 13 hours of daylight every day. You will feel extremely sweaty and uncomfortable in this high temperature and humidity level. Bringing an umbrella and apply plenty of sunscreens helps to prevent being soaking wet in the rain and getting sunburnt.
- Average temperature: 29°C
- Average sea Temperature: 30°C
- Monthly rainfall: 474mm
- Average hours of sunshine per day: 7
August:
August is still a hot month and may subject to seasonal storms. Nonetheless Halong Bay is still an attractive destination for the month since it will be a lot less crowded than the high season.
Continuing the streak of July, August in Halong carries the same level of rainfall for 16 wet days in the month. The average temperature though decreases slightly to 28.5°C, the heat and humidity are still rather uncomfortable. The sea temperature loses heat slower than on land so it is still at 30°C. The 13 hours of daylight has less sunshine since there is the only 6hrs of sunlight.
- Average temperature: 28.5°C
- Average sea Temperature: 30°C
- Monthly rainfall: 447mm
- Average hours of sunshine per day: 6
September:
September is a half-half month when the weather is no longer hot but not yet cold. It is an ideal time to visit Halong Bay.
September seems to be the transitional month from the blazing heat of summer to the more comfortable autumn. The average temperature drops to about 28°C with maximum temperature at noon is about 31°C and night temperature is as low as 25°C. The amount of rainfall though is still high; it is a significant decrease from July and August. The sea water temperature starts to cool down to 29°C.
- Average temperature: 28°C
- Average sea Temperature: 29°C
- Monthly rainfall: 328mm
- Average hours of sunshine per day: 6
October:
October is one of the best months to visit Halong Bay for the amiable weather.
If you plan to visit Halong bay and still want to dive in the refreshing water, October is the last month to go before it gets cold. The temperature is much more cool compare with the previous summer months, staying at 24.5°C on average. The amount of rainfall drops significantly distributing over 11 days. It is said that October is the perfect month to visit with reasonable heat and not too humid. 6 hours of sunshine is enough to get a few hundred beautiful snapshots of the bay.
- Average temperature: 24.5°C
- Average sea Temperature: 28°C
- Monthly rainfall: 86mm
- Average hours of sunshine per day: 6
November:
November starts seeing chilly wind but the dry weather may make the trip a lot better than one in the summer months.
Marking the start of dry season, November has a low amount of rainfall. The highest temperature reduces to 26°C and the lowest temperature is at 18°C. With this temperature and only 8 days of rain, the weather is cool and comfortable but can be a little chilly. The daylight hour shortens to only 11 hours/day and the sun shines overhead for about 5 hours. The sea temperature drops to 26°C, making it warmer than the on land temperature.
- Average temperature: 22°C
- Average sea Temperature: 26°C
- Monthly rainfall: 33mm
- Average hours of sunshine per day: 5
December:
December is a festive month and why not celebrate your important event in Halong Bay?
Winter officially arrives at Halong bay in December. The highest temperature reaches to only 22°C while the temperature can drop to about 15°C. The sea temperature continues to lower to 23°C. The dry season remains with very little rain and the number of wet days is only 7 days. There is only 5 hours of sunshine during the 11 hours of daylight in December. Visibility during December is quite low so photo-taking might be disappointing.
- Average temperature: 18.5°C
- Average sea Temperature: 23°C
- Monthly rainfall: 20mm
- Average hours of sunshine per day: 5