Ha Long Bay records about 1745mm of rain across roughly 118 wet days a year, which is a 32% chance on an average day. August is the wettest month at 310mm (18% of the annual total) and January the driest at 22mm. Local rain type: monsoon. Ha Long Bay's monsoon (May-September) brings heavy rain and reduced visibility. The limestone karsts are most dramatic emerging from mist, but typhoon risk is real.
Chance of rain on an average day: 32%
Rainfall climatology for Ha Long Bay. The live hour-by-hour answer for today loads at the top of this page from Open-Meteo and refreshes through the day — the figures below describe a typical year, not today.
Last updated: · Live forecast data refreshes hourly.
| Annual rainfall | 1745mm |
| Rain days per year | 118 |
| Odds on an average day | 32% |
| Wettest month | August — 310mm over 22 days |
| Driest month | January — 22mm over 2 days |
| Rain type | monsoon |
| Best dry window | October through December offers cool, clearer conditions for bay cruises. |
| Worst rain window | July and August bring the heaviest rain with typhoon risk. |
August delivers 1309% more rain than January (310mm vs 22mm). That gap is the difference between planning around showers and ignoring them.
No single month holds more than 18% of the annual total, so rain in Ha Long Bay is spread through the year — there is no season you can rely on being dry.
Ha Long Bay rain arrives in short, heavy bursts — shelter and timing matter more than gear.
Rain falls on about 22 days in August against 2 in January — the frequency swing matters more for planning than the millimetre totals.
Climate normals. Use them to judge whether today's live forecast at the top of the page is typical or unusual for the season.
| Month | Rainfall | Rain days | Chance on a given day | Highs |
|---|---|---|---|---|
| January | 22mm | 2 | 7% | 18°C |
| February | 28mm | 2 | 7% | 18°C |
| March | 42mm | 3 | 10% | 20°C |
| April | 85mm | 6 | 20% | 24°C |
| May | 180mm | 13 | 43% | 27°C |
| June | 225mm | 16 | 53% | 31°C |
| July | 265mm | 19 | 63% | 33°C |
| August | 310mm | 22 | 73% | 33°C |
| September | 245mm | 17 | 57% | 31°C |
| October | 165mm | 12 | 40% | 27°C |
| November | 72mm | 5 | 17% | 24°C |
| December | 32mm | 2 | 7% | 20°C |
Rain probability is the chance that at least 0.2mm falls at your location — not how long it rains. For Ha Long Bay we combine the hourly probability curve, expected volume in millimetres, and the city's own rainfall record into a single umbrella verdict.
| Factor | Weight | What it measures |
|---|---|---|
| Hourly probability | 40% | Peak and sustained chance of measurable rain across the next 24 hours. |
| Expected volume | 30% | Total millimetres, which separates a passing shower from a genuine soaking. |
| Timing & duration | 20% | When rain starts, when it eases, and the longest continuous dry window. |
| Local rain type | 10% | Drizzle, brief showers, thunderstorms or monsoon — each needs different gear. |
Live hourly values come from Open-Meteo and refresh through the day. Monthly rainfall figures are climate normals, so they describe a typical year rather than a forecast.
Ha Long Bay records rain on roughly 118 days a year — about a 32% chance on any given day — totalling around 1745mm.
August, with about 310mm over 22 rain days. That is 18% of the entire year's rainfall in a single month.
January is the driest month at 22mm across roughly 2 days. October through December offers cool, clearer conditions for bay cruises.
Ha Long Bay's monsoon (May-September) brings heavy rain and reduced visibility. The limestone karsts are most dramatic emerging from mist, but typhoon risk is real.
No. Probability is the chance that at least 0.2mm of rain falls at your location at some point in the period. Check the expected millimetres alongside it: 40% with 0.4mm is a passing shower, 40% with 12mm is a soaking.