The best time to visit Ha Long Bay, month by month

Ha Long Bay has two clear seasons. From May to September it is hot and humid, with average highs of 30 to 32 °C at Bai Chay, the cruise town on the bay, and most of the year’s rain: June to September bring 1,368 mm of the annual 1,923 mm. From November to April the north-east monsoon makes it cool and much drier, with average lows of 14 to 19 °C, and the sea drops to about 20 °C.

The two months between are the sweet spot. October still has the summer’s warmth, a high of 28.8 °C and 177 hours of sun, with half August’s rain days; November is drier still, 5.8 rain days, with a high of 25.5 °C and a sea of about 25 °C. The table gives the official climate averages for the Bai Chay weather station from Vietnam’s national building climate standard (QCVN 02:2022/BXD, data from the Institute of Meteorology, Hydrology and Climate Change), with average sea temperatures for Ha Long from World Sea Temperature, a private multi-year dataset rather than an official series.

Autumn gives the best balance of clear views, comfortable days on deck and water still warm enough to swim at Ti Top or Ba Trai Dao. Cloud cover is at its lowest of the year in October and November (about six tenths of the sky against nine in February and March), so the limestone islands stand out sharply, and the sunset tea on a day boat falls while you are still on the water, because the sun sets between about 17:10 and 17:50 from October to February.

It is also the cruise lines' peak season: the Ha Long and Bai Tu Long overnight adds a US$10 peak-season charge per person from 1 October to 30 April, as its listing states, and the cabins on the best-rated ships go first. The highest-rated overnight, the Elite ship with a panoramic pool, is from €113.39 with taxes and peak-season surcharges included for bookings made from 1 July 2026, rated 4.9 from more than 3,100 reviews; the best-value balcony cabin with a bathtub is from €99.79. For a day, the most-booked Ha Long day cruise is from €35.90, rated 4.8 from more than 14,900 reviews (all GetYourGuide, 15 Nov 2026).

Winter is the calm season: storms have never made landfall on this coast from December to April in the official 1961 to 2017 record, rain is light, and Ha Long’s limestone looks at its most atmospheric in soft grey light. December is the clearest of the cool months, with 128 hours of sun; February and March are the misty ones, with about 7 to 10 days of drizzle and 2 to 4 days of fog a month and the least sunshine of the year, 43 to 48 hours. Days are mild rather than cold, with highs of 19 to 22 °C, but it feels cooler on an open deck and in a kayak, and one listing advises warm clothes and a change of clothes from December to March.

The cruises that suit winter keep you warm on board. The Elite ship has a four-season pool, a spa and a sauna, from €113.39; the best-value balcony cruise puts a bathtub with a bay view in every cabin, from €99.79. For a day, the Amethyst luxury day boat has a four-season jacuzzi for up to 20 adults on its sundeck, from €46.35, and the Ha Long to Lan Ha day cruise has a heated jacuzzi and a floating pool, from €44.56 (GetYourGuide, 15 Nov 2026). The sea is about 20 °C from January to March, so a swim is for the hardy.

Summer is the season for the water. The sea is about 27 to 30 °C from May to September, kayaking in the Lan Ha lagoons is warm work rather than cold, and the days are long, with at least 165 hours of sunshine every month. Rain usually comes as heavy showers and thunderstorms (Bai Chay averages 8 to 11 thunderstorm days a month from June to August) rather than all-day grey, and the bay is green and lush.

It is also Vietnam’s school holiday season. The best-selling day cruise’s own listing says the bay is busiest from June to August and at weekends, so a weekday in May, June or September is the better pick. Lan Ha Bay, south of Ha Long, sees fewer day boats; the Taliya yacht day cruise to Lan Ha, with a bamboo boat through Dark and Bright Cave and a swim at Ao Ech, is from €51.79, and the small-group Lan Ha kayak day from Cat Ba is from €29.34 (GetYourGuide, 15 Nov 2026).

Vietnam’s storm season runs from June to November, and storms reach the Quang Ninh to Thanh Hoa coast, which includes Ha Long Bay and Hai Phong’s Lan Ha Bay, mostly from June to September. In the official record for 1961 to 2017 that coast averaged 1.79 landfalls of a storm or tropical depression a year, with July (0.54) and August (0.47) the most likely months and October and November rare (QCVN 02:2022/BXD, Table B.1). A storm that passes nearby without landing can still close the bay for a day or two.

The decision is the province’s, not the cruise lines'. Under Quang Ninh’s tourist-boat rules, the waterway port authority issues every boat a permit to leave port, based on the boat’s class and the Quang Ninh hydro-meteorological forecast, and refuses it when dangerous weather is forecast or the wind is above what the boat is built for (Decision 4088/2015, in force until Decision 43/2024 replaced it on 20 October 2024). A closure is announced the day before or the morning of a storm, as press reports of recent storms show: for Typhoon Maysak on 3 July 2026 (Thanh Nien), overnight and evening boats lost their permits from 12:00 and all other boats from 17:00, with permits back after the final storm bulletin. For Typhoon Wipha, every tourist boat on the bay lost its permit to leave port from 20 July 2025, with no sailings expected before the end of 22 July (SGGP and Dan Tri). Hai Phong closes Lan Ha Bay by its own order: from 07:00 on 22 August 2026 it banned tourist boats from the sea for a tropical depression (Bao Phap Luat). Strong wind outside the storm season can stop boats for a morning: on 1 May 2022 the port authority held departures in force 4 to 5 northerly winds, gusting 6 to 7, and let them sail again at about 11:00 (VOV).

All 28 cruises and tours we list can be cancelled up to 24 hours in advance for a full refund, and all offer reserve now, pay later, so in the storm months you can book a cabin, watch the forecast and cancel the day before if a storm is coming (GetYourGuide, 15 Nov 2026). Twelve of the 28 listings say the itinerary may change with the weather or the tides, which usually means a swap of cave, lagoon or kayak stop rather than a cancellation.

Two listings spell out what happens in a storm. The Taliya day cruise says it may be cancelled without notice in major climatic events and that you will be offered a full refund if it is cancelled. The Cat Ba kayak and snorkelling boat tour runs rain or shine but is cancelled if there is a storm. For a storm-month booking, those two plus free cancellation are the terms to read before you pay.

Vietnamese holidays fill the boats and the expressway from Hanoi, and 14 of our 28 listings add a holiday surcharge. Tet, the Lunar New Year, is the big one: the first day is Saturday 6 February 2027, and the Ministry of Home Affairs has set a seven-day public holiday from Thursday 4 to Wednesday 10 February 2027 (Notice 11483/TB-BNV, 9 October 2026). Two listings name 5 to 8 February 2027 as their Tet surcharge days.

If you travel over Christmas or New Year, book early: two of the 5-star balcony cruises charge a gala dinner surcharge of US$40 per person on Christmas Eve and New Year’s Eve, and US$5 at Tet. Four of our overnight cruises list no holiday surcharge at all, among them the best-value balcony and bathtub cruise from €99.79 and the small-group Lan Ha cruise from Cat Ba from €113.87 (GetYourGuide, 15 Nov 2026).