Bai Tu Long Bay has the humid subtropical climate of northern Vietnam: a hot, wet summer with a typhoon risk, and a cool, often misty winter. There is no month when cruises stop entirely, but the most reliable conditions are October to early December and March to May.
Bai Tu Long Bay month by month
| Month | Day / night (approx.) | Conditions | Verdict |
|---|---|---|---|
| January | 19 / 13 °C | Cool, grey, drizzle | Atmospheric but chilly; Tet holiday may fall here |
| February | 19 / 14 °C | Mist and drizzle | Moody mist; Tet crowds some years |
| March | 22 / 17 °C | Mist lifting | Improving; soft light |
| April | 26 / 21 °C | Warm, some haze | Very good |
| May | 30 / 24 °C | Hot, water warming | Good — swimming starts |
| June | 31 / 26 °C | Hot, humid, showers | Fine for swimming; Vietnamese holidays |
| July | 32 / 26 °C | Rain, typhoon risk | Book flexible; storms possible |
| August | 31 / 26 °C | Wettest, typhoon risk | Highest cancellation risk |
| September | 30 / 25 °C | Rain easing, typhoon risk | Mixed; improves late month |
| October | 28 / 22 °C | Dry, clear, warm | Our favourite month |
| November | 25 / 18 °C | Dry, clear, mild | Excellent |
| December | 21 / 15 °C | Cool, mostly dry | Good, bring a jacket |
Autumn: October to early December — the best of the year
The typhoon season fades, humidity drops and the skies clear. Days are warm, the sea is still pleasant for swimming in October, and visibility across the karsts is at its best. This is peak season for international visitors, so book good boats a few weeks ahead.
Spring: March to May — the other sweet spot
Winter mists lift through March, April is warm and settled, and by May the water is warm enough to swim. Light haze can soften the views, which photographers often love.
Summer: June to September — hot, green, and a typhoon gamble
Hot and humid with heavy showers, and the season of Vietnamese family holidays. Swimming and kayaking are at their best, but tropical storms can bring cancellations, most often in August and September. Book with free cancellation and keep a spare day in your plans.
Winter: December to February — cool and misty
Temperatures drop to the high teens by day, drizzle and mist are common, and swimming is off the agenda. The upside is atmosphere: karsts fading into fog, quieter boats and lower prices outside the Tet (Lunar New Year) holiday.
When to avoid
- Tet (Lunar New Year), usually late January or February — prices rise and transport is packed.
- 30 April – 1 May and 2 September national holidays — domestic crowds, especially on Quan Lan and Co To.
- Peak typhoon weeks in August–September if your dates are fixed and cannot move.
Best time for the islands
For beach time on Quan Lan or Co To, aim for May–June or September–October, avoiding summer weekends. Winter crossings can be rough and are sometimes cancelled.
