Independent guidelanhabay.cruises is an independent guide to Lan Ha Bay. We are not the website of any cruise line, tour operator, port or government office. Some links are affiliate links: if you book through them we may earn a commission at no extra cost to you.
EN

PlanPlanning · weather and seasons

Best time to visit Lan Ha Bay: weather, storms and crowds by month

The best time to visit Lan Ha Bay is October and November: the driest, sunniest stretch of the year with the sea still warm enough to swim. December and January are dry but cool, February to April is grey and misty, and May to September is hot, wet and the time when storms stop the boats.

Best months
October and November
Driest month
December (23 mm), then November (43 mm)
Wettest month
August (353 mm)
Fog and drizzle
February to April
Storm season
June to November
Warmest sea
June to August, about 30 °C
Busiest days
30 April–1 May, summer weekends, Tet

Updated October 16, 2026Facts checked against official sourcesContains affiliate links

Best time to visit: what you can book

9 options · Prices checked on October 16, 2026

Length

Platform

See everything on GetYourGuide →See everything on Klook →

The best time to visit Lan Ha Bay is October to November. Rain drops sharply after September, the sun is out for 150–180 hours a month, and the sea is still 25–28 °C. If you can only travel at another time, the bay still works all year: what changes is the light, the water temperature and the chance that a storm cancels your cruise.

The numbers below come from the long-term normals of the Phu Lien weather station in Hai Phong, the nearest station with a long record, and a 10-year sea-temperature average for Cat Ba. Lan Ha (vịnh Lan Hạ, the bay east of Cat Ba Island) is on the same stretch of coast, so the pattern is the same.

Lan Ha Bay weather by month

Cat Ba weather, month by month
JanFebMarAprMayJunJulAugSepOctNovDec
High °C202022263132323231292622
Low °C141518212426262524221916
Sea °C201921242830303030282522
Rain mm282749852022382383532571364323
Rainy days813171313141418141066

Source: Air temperature and rain: Phu Lien station, Hai Phong (Vietnam Institute for Building Science and Technology long-term normals, via Wikipedia 'Haiphong'). Sea temperature: Cat Ba 10-year average, seatemperature.info.

Month High / low °C Rain Sun hours Sea °C
January 19.8 / 14.2 28 mm 82 19.6
February 20.1 / 15.2 27 mm 47 19.2
March 22.2 / 17.7 49 mm 41 20.9
April 26.4 / 21.1 85 mm 85 24.0
May 30.6 / 24.1 202 mm 184 27.8
June 32.0 / 25.6 238 mm 181 30.0
July 32.1 / 25.9 238 mm 199 30.3
August 31.5 / 25.3 353 mm 170 30.3
September 30.8 / 24.3 257 mm 179 29.8
October 29.0 / 22.0 136 mm 180 28.0
November 25.8 / 18.8 43 mm 149 25.2
December 22.1 / 15.5 23 mm 127 21.9

What the table shows that brochures skip: March has 17 rain days but only 49 mm of rain. That is drizzle (mưa phùn) and low cloud, not downpours, with humidity around 90%. February and March have the least sunshine of the year, 41–47 hours a month.

What each month is good for
JanFebMarAprMayJunJulAugSepOctNovDec
Cruise weather overallGoodPoorPoorGoodGoodPoorPoorPoorPoorBestBestGood
Clear views and photosPoor00PoorGoodGoodBestGoodGoodBestGoodGood
Swimming000PoorGoodBestBestBestBestBestGoodPoor
Plankton nights000PoorGoodGoodGoodGoodGoodGood00
Deep-water solo climbing00PoorGoodGoodGoodGoodGoodBestBestBestPoor
Hiking in the national parkBestGoodGoodGoodPoorPoorPoorPoorPoorGoodBestBest
Fewer domestic crowdsGoodPoorBestGoodPoorPoorPoorGoodGoodBestBestBest

PoorGoodBest

The seasons in Lan Ha Bay

October and November: the best time

These are the driest sunny months: October gets 136 mm of rain and 180 hours of sun, November 43 mm and 149 hours. The sea is 28 °C in October and 25 °C in November, so swim stops still feel good. Storm season officially runs until November, so flexible booking still makes sense. This is the time for a 3-day cruise if you can afford the extra night: more daylight hours on the water pay off when the sky is clear.

December and January: dry and cool

Rain is minimal (23 mm in December, 28 mm in January), but daytime highs are around 20–22 °C and nights drop to 14–16 °C. The sea is about 20 °C, so few people swim. Sundecks are chilly in the evening; bring a warm layer. In exchange you share the bay with fewer domestic travelers. Christmas Eve and New Year's Eve carry gala-dinner surcharges on many ships, often USD 40–60 per person.

February to April: fog and drizzle

This is the grey season. Expect karst islands fading into mist rather than blue-sky photos, and fine drizzle on many days. Sea mist is beautiful in its own way, but if your trip is about swimming or sharp views, avoid February and March. April warms up (26 °C highs, sea 24 °C) and is a reasonable shoulder month.

May to September: hot, wet and stormy

Every month from May to September gets more than 200 mm of rain, and August is the wettest at 353 mm. The sea is at its warmest, around 30 °C from June to August. This is also the Vietnamese holiday season and the period when storms cancel sailings. Book flexible, and read the next section.

Storm season: how cancellations work

The storm season for northern Vietnam is June to November, according to the national disaster agency; some operators flag May to July as their most affected months. When a storm approaches, the authorities stop the boats, not the cruise line: in Quang Ninh (Ha Long side) the Inland Waterway Port Authority stops issuing departure permits, and Hai Phong issues a sea ban (cấm biển) and stops the Cat Ba ferries.

Two recent examples show what that means in practice:

  • On 22 August 2026, with Storm No. 4, the sea ban left more than 1,700 tourists stranded on Cat Ba (VnExpress).
  • On 13–14 September 2026 the car ferry stopped at about Beaufort 4 winds, and travelers waited 7–12 hours to leave the island (VnExpress).

There is no state refund rule. Refunds follow the operator's or platform's terms. A typical operator rule is a 100% refund if the cruise is cancelled before sailing, and payment only for services used if it is cut short; some ships also convert a cancelled overnight into a day trip. On GetYourGuide most cruise listings allow free cancellation up to 24 hours before the start, which is the safest way to book in storm season. Our how to book guide compares the platforms with direct terms.

Cruises that check in at Tuan Chau in Ha Long avoid the Cat Ba ferry entirely, which matters when the ferry is the bottleneck. A storm that stops the ships stops them on both sides, though.

Crowds and holidays

There are no official visitor counts comparing months, but Vietnamese holidays are easy to spot on the water and at the ferry:

  • 30 April and 1 May. Cat Ba received about 70,000 visitors in those two days in 2026, with a 2 km queue at the car ferry at 05:00.
  • Summer weekends. VnExpress calls May to July the peak season for Cat Ba (travel guide).
  • Tet (Lunar New Year), in late January or February. Many ships add a surcharge: a flat USD 40–60 per person or a percentage on the fare.
  • 2 September (National Day). A long weekend for Vietnamese travelers; in 2026 it was quiet because visitors feared being stranded after the storms.

International visitors are more common from October to April. If you want quiet water and an easy ferry, aim for October, November or March on weekdays.

Best time for each activity

Swimming

Swim stops are part of most cruises from May to October, when the sea is 28–30 °C. November is still fine for most people at 25 °C. From December to March the water is 19–21 °C.

Bioluminescent plankton

The glow appears in the warm months, roughly May to October, on dark, moonless, calm nights. It is never guaranteed: a bright moon, town lights and squid-boat lamps all wash it out. Plan around the new moon:

Darkest nights for the glowing plankton
Best windowNew moonFull moon (weakest)
Nov 7 – Nov 13Nov 10Nov 24
Dec 6 – Dec 12Dec 9Dec 24
Jan 5 – Jan 11Jan 8Jan 23
Feb 3 – Feb 9Feb 6Feb 21
Mar 5 – Mar 11Mar 8Mar 23
Apr 3 – Apr 9Apr 6Apr 21
May 3 – May 9May 6May 21
Jun 1 – Jun 7Jun 4Jun 19
Jul 1 – Jul 7Jul 4Jul 19
Jul 30 – Aug 5Aug 2Aug 17
Aug 29 – Sep 4Sep 1Sep 16
Sep 28 – Oct 4Oct 1Oct 15
Oct 27 – Nov 2Oct 30Nov 14
Nov 26 – Dec 2Nov 29Dec 13

The glow shows best on moonless, calm nights; it is never guaranteed. Dates in Vietnam time.

Every plankton outing relies on night kayaking or swimming, so the kayak suspension below applies. Details in our plankton guide.

Kayaking

Season is not the main question here. Kayaking in the Cat Ba bays has been under an official suspension since November 2024, re-confirmed in late 2025 (VnExpress). Some ships offer it only in a designated area or replace it with a bamboo boat, tender or swim. Ask the operator in writing. See kayaking in Lan Ha.

Deep-water solo climbing

Deep-water solo needs a high tide, and Lan Ha has only one high tide a day, with a range of up to 3 m. The best tides fall from June to November; April–May and September–November are the best compromise between tides and weather. Winter suits sport climbing on land better. More in rock climbing.

Hiking in Cat Ba National Park

The forest trails to Ngu Lam peak are hot and humid from May to September. December to March is more comfortable, and October–November combines dry trails with clear views. The park is open 07:00–17:00 (park ticket page). See Cat Ba National Park.

Winter and summer timetables

The season changes more than the weather:

  • Cat Ba car ferry. From 1 September 2026 the last boat leaves Cat Ba at 17:30 and the mainland at 18:00, 30 minutes earlier than in summer.
  • Tuan Chau – Gia Luan ferry. The last boat from Tuan Chau leaves at 15:30 in summer and 15:00 in winter, and only sails with at least 30 passengers.
  • Inter-bay ships. Ships on the four licensed routes between Ha Long and Lan Ha start from 05:00 and must be back before 20:00 in summer; in winter, from 05:30 and back before 19:00.
  • Cruise programmes. Some ships change the route by season. Paradise Grand, for example, does Ao Ech (Frog Lake) on its summer programme and Viet Hai village in winter; see the Paradise Grand review.

What to book, season by season

  • October–November: any ship works. Book early for weekends, and consider a 3-day programme.
  • December–January: if you want to use a pool, pick a ship whose pool is open all year, such as Elite of the Seas or the semi-indoor pool on Celina of the Sea; a one-night cruise is enough.
  • February–April: go for the atmosphere and lower demand outside Tet; keep the plan simple, as views may be limited.
  • May–September: book on a platform with free cancellation, travel midweek, and keep a buffer day before flights. A day cruise from Cat Ba is a low-risk option if you are already on the island.

See everything on GetYourGuide →See everything on Klook →Prices checked on October 16, 2026

FAQ

What is the best month to visit Lan Ha Bay?

October or November. They are the driest sunny months, with 136 mm and 43 mm of rain and a sea of 28 °C and 25 °C.

Is it worth visiting Lan Ha Bay in winter?

Yes, if you accept cool weather. December and January are dry, with highs around 20–22 °C and lows of 14–16 °C, but the sea is about 20 °C, so swimming is for the brave.

When is typhoon season in Lan Ha Bay?

June to November, according to the national disaster agency. In 2026 storms stopped the Cat Ba ferries on 22 August and 13–14 September. Keep a buffer day before flights.

Will my cruise be cancelled if a storm comes?

If the port authorities stop departures, yes, on every ship. Refunds follow the operator's or platform's terms; a full refund before sailing is the usual operator rule.

Is Lan Ha Bay foggy in spring?

February to April is the misty, drizzly season. February and March have the lowest sunshine of the year, 41–47 hours a month.

When can you see the bioluminescent plankton?

In the warm months, roughly May to October, on dark, moonless and calm nights. It is never guaranteed.

Keep exploring

PlanLan Ha vs Ha Longfrom $28 PlanHow to bookfrom $110 Getting thereHow to get there Getting thereCruise piersfrom $110 PlanHomefrom $28