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weather on the water

Halong Bay weather by month: rain, fog, sea and boat hours

Halong Bay weather, in Vietnam's far north-east, splits into a cool, dry winter and a hot, wet summer. At Phu Lien, the long-record weather station on the Hai Phong coast, January averages 17°C (63°F) and July 29°C (84°F), and August is the wettest month with 346 mm. Fog peaks in March. The sea south of Cat Ba Island runs from 19°C (66°F) in February to 30°C (86°F) in August. Boats keep winter hours from 1 November to 31 March and summer hours from 1 April to 31 October.

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the year at a glance

Halong Bay weather month by month

Pick your month for the weather in Halong Bay, Vietnam, as the nearest stations record it: temperature, rain, fog, the sea and the storms, with the boat hours that apply. Each month has its own row and link, so you can share the line for your trip.

Rain and temperature by month at Phu Lien Bars show monthly rain, lowest from December to February and highest in August. Two lines show the mean temperature and the mean daytime high, coolest in January and warmest in June and July. A strip under the months marks winter boat hours from November to March and summer boat hours from April to October. The table below gives every value.
Rain Mean temperature Daytime high Phu Lien station (Hai Phong), NOAA Global Summary of the Day, 1996 to 2024. Boat hours under Quang Ninh Decision 43/2024.
Halong Bay weather by month, station by stationTemperature, rain and fog at Phu Lien and Bach Long Vi, 1996 to 2024 (NOAA Global Summary of the Day); sea surface south of Cat Ba Island, 1991 to 2020 (NOAA OISST); storm systems whose track came within 150 km to 350 km of the bay, 1991 to 2025 (IBTrACS)
Month Mean temperaturePhu Lien Daytime highPhu Lien RainPhu Lien Days with rainPhu Lien, 1 mm or more Fog daysPhu Lien, coast Fog daysBach Long Vi, offshore Sea surfacesouth of Cat Ba Island Storm systemstracks near the bay Boat hoursHalong and Bai Tu Long Bay
January 17°C (63°F) 20°C (68°F) 34 mm 5 days 1.6 days 2.5 days 20°C (68°F) none in 35 years 5:30 to 19:00winter
February 18°C (64°F) 21°C (70°F) 28 mm 6 days 2.4 days 5.7 days 19°C (66°F) none in 35 years 5:30 to 19:00winter
March 20°C (68°F) 23°C (73°F) 53 mm 10 days 3.7 days 8.6 days 20°C (68°F) none in 35 years 5:30 to 19:00winter
April 24°C (75°F) 27°C (81°F) 71 mm 7 days 1.2 days 4.2 days 23°C (73°F) 0 to 1 in 35 years 5:00 to 20:00summer
May 27°C (81°F) 31°C (88°F) 190 mm 10 days under 1 day under 1 day 27°C (81°F) none in 35 years 5:00 to 20:00summer
June 29°C (84°F) 33°C (91°F) 207 mm 10 days under 1 day 0 days 29°C (84°F) 5 to 11 in 35 years 5:00 to 20:00summer
July 29°C (84°F) 32°C (90°F) 260 mm 13 days 0 days 0 days 30°C (86°F) 21 to 32 in 35 years 5:00 to 20:00summer
August 28°C (82°F) 32°C (90°F) 346 mm 14 days under 1 day 0 days 30°C (86°F) 15 to 29 in 35 years 5:00 to 20:00summer
September 27°C (81°F) 31°C (88°F) 257 mm 12 days under 1 day 0 days 29°C (84°F) 14 to 31 in 35 years 5:00 to 20:00summer
October 25°C (77°F) 29°C (84°F) 92 mm 6 days under 1 day 0 days 28°C (82°F) 6 to 19 in 35 years 5:00 to 20:00summer
November 22°C (72°F) 27°C (81°F) 45 mm 4 days 0.5 days under 1 day 26°C (79°F) 2 to 5 in 35 years 5:30 to 19:00winter
December 18°C (64°F) 22°C (72°F) 26 mm 4 days 0.9 days under 1 day 22°C (72°F) none in 35 years 5:30 to 19:00winter

Phu Lien, Bach Long Vi, the open sea

Which station each figure describes

No weather station on the bay itself has a long public record. The WMO climate normals for 1991 to 2020, as archived by NOAA, list no station in Vietnam, so there are no official normals for Bai Chay, Tuan Chau or Cat Ba. The figures here come from two stations in NOAA's Global Summary of the Day instead, averaged over 1996 to 2024.

Phu Lien is a coastal station in Hai Phong, west of the bay. Its temperature, rain and fog describe the mainland coast rather than the open water. Bach Long Vi is an island far out in the Gulf of Tonkin; its fog days show what the open sea does, and in late winter and spring it records fog on more days than the coast.

The sea surface temperature is the 1991 to 2020 mean for the open-water grid cell just south of Cat Ba Island in NOAA's OISST record. Water close to the shore and inside the bay can differ, cooler in winter. Storm counts are tracks from NOAA's IBTrACS archive, 1991 to 2025, that came within 150 km to 350 km of the middle of Halong Bay. All of it, as files, is on the data page.

Bai Tu Long Bay seascape
Karst islands in gray morning light in Bai Tu Long Bay.Photo: Benjamin Smith / Wikimedia Commons, CC BY-SA 4.0

dry and cool

Winter weather in Halong Bay, November to March

From November to March the weather in Halong Bay is dry and cool. January is the coldest month at Phu Lien, with a mean of 17°C (63°F) and daytime highs around 20°C (68°F). December is the driest, with 26 mm of rain on 4 days. The sea is at its coolest in February, at 19°C (66°F) south of Cat Ba Island. Wind on an open deck makes it feel cooler than the station figure, so pack a warm layer.

Winter is also when boats keep shorter hours. Under Quang Ninh Decision 43/2024, tourist boats on Halong Bay and Bai Tu Long Bay may sail from 5:30 to 19:00 between 1 November and 31 March. The Cat Ba bays, which include Lan Ha Bay, keep a similar winter window under Hai Phong Decision 253/2025: boats must be back in port by 19:00. A day cruise has to fit inside these hours.

Storm tracks are rare in winter. From December to March no storm or tropical depression came within 350 km of the bay in 1991 to 2025; November had 2 to 5 in 35 years, counting tracks within 150 km to 350 km.

Halong Bay in mist or fog
Karst islands and a wooden junk reflected in still water in early morning mist.Photo: aschaf / Wikimedia Commons, CC BY 2.0

haze and fog

Fog and haze, February to April

Fog is the weather that most often hides the islands. At Phu Lien it peaks in March, with fog on 3.7 days of the month, against 2.4 days in February and 1.2 days in April. Out at sea it is more frequent: Bach Long Vi records fog on 8.6 days in March. From May to October fog is close to absent at both stations.

A 2022 study by the Northeast Regional Hydro-Meteorological Station, using 2014 to 2019 observations, found that sea fog at Cua Ong and Co To in Quang Ninh occurs mainly from December to April. At Hon Dau on the Hai Phong coast, the station in that study nearest to Lan Ha Bay, it found fog mainly from February to April. Both fit the station counts above: fog belongs to late winter and spring.

What fog changes: Quang Ninh's rules set no visibility limit for tourist boats. When the weather is not safe to go on, which the rules describe as rain, fog or strong wind, the captain tells the passengers and moves the boat to shelter, and the Inland Waterway Port Authority grants or holds the departure permits.

April to October

Summer weather: heat, rain and the storm months

From May the weather turns hot and humid. June and July are the warmest months at Phu Lien, with means of 29°C (84°F) and 29°C (84°F), and June daytime highs average 33°C (91°F). The sea warms to 30°C (86°F) by August. Rain builds from May and peaks in August with 346 mm on 14 days. The UK Foreign, Commonwealth and Development Office states that the rain season in northern Vietnam runs from June to September.

Summer boat hours are longer: tourist boats on Halong Bay and Bai Tu Long Bay may sail from 5:00 to 20:00 between 1 April and 31 October, and boats on the Cat Ba bays must be back in port by 20:00.

Wide Halong Bay seascape with karst islands
Three limestone stacks standing in calm water under cumulus cloud.Photo: Christophe95 / Wikimedia Commons, CC BY-SA 4.0

The storm season, as each government states it

  • The UK FCDO states that the tropical storm season in Vietnam normally runs from May to November.
  • Australia's Smartraveller states that the storm season is usually from June to November.
  • The US Department of State states that storms hit the central and northern coasts from June to December, with the worst storms typically from September to November.

For this stretch of coast the peak is narrower. Vietnam's Institute of Meteorology, Hydrology and Climate Change found that July, August and September together carry 76% of the storms and tropical depressions that affected the Quang Ninh to Thanh Hoa coast in 1961 to 2014. In the track archive, September had 14 to 31 in 35 years within 150 km to 350 km of the bay. For a cruise with one night on board that starts in September, the odds that a storm stop overlaps it run 4% to 8%; the best time to visit Halong Bay page gives these odds for every month and length of cruise.

hours, squalls, storm stops

What the weather changes on board

Weather on Halong Bay changes the day in three ways: the hours the boats may sail, short holds for squalls, and full stops for storms. None of them comes with a promise either way; the authorities decide on the day.

When tourist boats may sailQuang Ninh Decision 43/2024 (Halong Bay, Bai Tu Long Bay); Hai Phong Decision 253/2025 (Cat Ba bays, including Lan Ha Bay)
SeasonHalong Bay and Bai Tu Long BayLan Ha Bay and the Cat Ba bays: back in port by
Summer, 1 April to 31 October5:00 to 20:0020:00
Winter, 1 November to 31 March5:30 to 19:0019:00

Squalls. Since mid-2026 a warning service run with the Northern Region Hydro-Meteorological Station splits Halong Bay and Bai Tu Long Bay into nine zones and warns of thunderstorms, squalls and lightning minutes ahead, so a hold can cover one zone instead of the whole bay. Its address is https://halong.navy01.com/. These same-day holds are not posted afterwards.

Storm stops. When a storm or tropical depression is forecast, departures are stopped by the Quang Ninh Inland Waterway Port Authority until the final national storm bulletin. The cruise suspensions log lists every stop the Ha Long Bay Management Board has posted, with its start, end and length. If a stop falls on your dates, what happens to your booking is whatever the operator or booking site states in its terms. On a cruise with a night on board, check those terms before you pay.

the south side

Cat Ba Island weather and Lan Ha Bay

Cat Ba Island weather follows the same year as Halong Bay: there is no long-record station on the island, and Phu Lien on the coast to the west and Bach Long Vi out at sea frame it. The sea temperature in the table is the cell just south of Cat Ba Island, so it is the nearest sea figure for Lan Ha Bay, measured in open water rather than in a sheltered cove.

Fog on the Hai Phong side has the shorter season of the two in the 2022 study, mainly February to April at Hon Dau. Boats on the Cat Ba bays keep their own hours under Hai Phong's rules, back in port by 19:00 in winter. How to reach the island and where to stay is in the Cat Ba Island guide.

Cat Ba town harbour
Fishing and tour boats moored along the Cat Ba town waterfront at dusk.Photo: Christophe95 / Wikimedia Commons, CC BY-SA 4.0

questions

Questions about Halong Bay weather

Is it cold on a Halong Bay cruise?

In winter it can be. At Phu Lien, the nearest long-record station, January averages 17°C (63°F), and the sea south of Cat Ba Island cools to 19°C (66°F) in February. Wind on an open deck makes it feel colder. From May to October the weather is hot, with daytime highs of 33°C (91°F) in June.

What is the weather like in Halong Bay in January?

Cool and mostly dry. Phu Lien records a mean of 17°C (63°F), daytime highs around 20°C (68°F) and 34 mm of rain on 5 days. Fog comes on 1.6 days at Phu Lien. Boats keep winter hours, 5:30 to 19:00 on Halong Bay and Bai Tu Long Bay.

What is the best month for weather in Halong Bay?

It depends on what you trade. December to March is the driest stretch at Phu Lien, with no storm track near the bay on record; February to April has the most fog; May to September is hot and wet, and July to September carries most of the storms. The best time to visit page sets the storm odds for each month.

Do storms cancel Halong Bay cruises?

They can stop them. The Quang Ninh Inland Waterway Port Authority stops departures when a storm or tropical depression is forecast, until the final national bulletin, and captains move boats to shelter when the weather turns. The suspension log lists each posted stop. Refunds are whatever your operator or booking site states.

How is the weather in Halong Bay now?

This guide gives the record by month, not a live forecast. For the day itself, the national hydro-meteorological service publishes storm bulletins, the squall warning service for Halong Bay and Bai Tu Long Bay posts zone warnings, and the Ha Long Bay Management Board posts the port authority's stop notices.

Sources

  1. Under Quang Ninh Decision 43/2024/QĐ-UBND, when weather becomes unsafe the captain must tell passengers and move the boat to shelter, and the decision to grant a port departure permit rests with the Inland Waterway Port Authority (Cảng vụ). Quang Ninh Provincial People's Committee, Decision 43/2024/QĐ-UBND of 8 Oct 2024 (in force 20 Oct 2024), Regulation on managing inland waterway vessels serving tourists on Halong Bay and Bai Tu Long Bay, 8 October 2024.
  2. Smartraveller states the storm season in Vietnam is usually June to November months. Australian Government DFAT, Smartraveller, Vietnam travel advice (updated 24 Sep 2026, still current 14 Nov 2026), 24 September 2026.
  3. The US Department of State states storms hit Vietnam's central and northern coasts from June to December, with the worst storms typically in September to November months. US Department of State, Vietnam travel advisory and country information (page last updated 2 Jul 2026; advisory issued 24 Jun 2026), 2 July 2026.
  4. Under Hai Phong Decision 253/2025/QĐ-UBND, in summer (1 Apr to 31 Oct) tourist boats on the Cat Ba bays may leave port from 5:00 and must be back in port by 20:00 local time. Hai Phong City People's Committee, Decision 253/2025/QĐ-UBND (31 Dec 2025), Regulation on tourism and tourist boats on the Cat Ba bays, full text as reproduced by thuvienphapluat.vn, 31 December 2025.
  5. Under Hai Phong Decision 253/2025/QĐ-UBND, in winter (1 Nov to 31 Mar) tourist boats on the Cat Ba bays may leave port from 5:30 and must be back in port by 19:00 local time. Hai Phong City People's Committee, Decision 253/2025/QĐ-UBND (31 Dec 2025), Regulation on tourism and tourist boats on the Cat Ba bays, full text as reproduced by thuvienphapluat.vn, 31 December 2025.
  6. The UK FCDO states the tropical storm season in Vietnam normally runs May to November months. UK Foreign, Commonwealth & Development Office, Foreign travel advice: Vietnam, 21 September 2026.
  7. The UK FCDO states the rain season in northern Vietnam runs June to September months. UK Foreign, Commonwealth & Development Office, Foreign travel advice: Vietnam, 21 September 2026.
  8. Storm-track counts by month for the Gulf of Tonkin can be built from IBTrACS v04r01 (NOAA NCEI) Western Pacific best tracks; the saved subset covers 17-23N, 105-110E and holds a count of systems of 596 tropical systems. NOAA NCEI, International Best Track Archive for Climate Stewardship (IBTrACS) v04r01, WP basin CSV, file dated 2026-11-12, 12 November 2026.
  9. Daily fog flags, visibility, rain and temperature for the nearest synoptic stations (Phu Lien in Hai Phong, Bach Long Vi offshore, Mong Cai) are in NOAA's Global Summary of the Day; saved years run 1996 to the data end date 24 August 2025. NOAA NCEI, Global Summary of the Day (GSOD), stations 48826099999, 48839099999, 48838099999, 24 August 2025.
  10. Viet Nam is not among the countries in the WMO 1991-2020 Climatological Standard Normals archived by NOAA NCEI (accession 0253808), so official 1991-2020 normals for Bai Chay are not available from that dataset; Vietnam station count in it is 0 stations. NOAA NCEI, WMO Climatological Standard Normals 1991-2020, accession 0253808, Region II folders (versions 1.1 and 6.6), 14 November 2026.
  11. A 2022 study by the Northeast Regional Hydro-Meteorological Station, using 2014-2019 observations, found that sea fog at Cua Ong and Co To (Quang Ninh) occurs mainly in the months December to April. Lanh Nguyen Viet and Doan Phan Van, 'Nghiên cứu dự báo sương mù vùng biển Quảng Ninh - Hải Phòng', Tạp chí Khoa học Tài nguyên và Môi trường no. 41, 2022, 14 July 2022.
  12. The same 2022 study found fog at Hon Dau station (Hai Phong coast, nearest station to Lan Ha Bay in the study) occurs mainly in February to April months. Lanh Nguyen Viet and Doan Phan Van, 'Nghiên cứu dự báo sương mù vùng biển Quảng Ninh - Hải Phòng', Tạp chí Khoa học Tài nguyên và Môi trường no. 41, 2022, 14 July 2022.
  13. In summer (1 April to 31 October) tourist boats on Halong Bay and Bai Tu Long Bay may leave port from 5:00 and must be back by 20:00, under Quang Ninh Decision 43/2024/QD-UBND 5:00 to 20:00 local time. Quang Ninh Provincial People's Committee, Decision 43/2024/QD-UBND, Article 14(1), 8 October 2024.
  14. In winter (1 November to 31 March) tourist boats on Halong Bay and Bai Tu Long Bay may leave port from 5:30 and must be back by 19:00, under Quang Ninh Decision 43/2024/QD-UBND 5:30 to 19:00 local time. Quang Ninh Provincial People's Committee, Decision 43/2024/QD-UBND, Article 14(2), 8 October 2024.
  15. Quang Ninh Decision 43/2024/QD-UBND sets no numeric wind or visibility threshold; when weather is unsafe the captain moves the boat to shelter and the port authority tells boats where to shelter, so the stated trigger is weather not safe to continue the journey. Quang Ninh Provincial People's Committee, Decision 43/2024/QD-UBND, Article 7(5) and 7(6), 8 October 2024.
  16. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in January for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 20.0 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  17. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in February for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 19.4 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  18. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in March for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 20.3 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  19. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in April for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 23.0 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  20. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in May for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 27.0 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  21. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in June for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 29.2 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  22. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in July for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 29.6 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  23. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in August for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 29.7 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  24. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in September for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 29.4 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  25. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in October for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 27.9 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  26. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in November for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 25.5 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  27. NOAA OISST v2.1 gives the 1991-2020 mean sea surface temperature in December for the Gulf of Tonkin grid cell at 20.625N 107.125E (open water south of Cat Ba Island, nearest ocean cell to Halong Bay) as 22.4 degrees C. NOAA NCEI Optimum Interpolation SST v2.1 (daily, 0.25 degree), dataset ncdcOisst21Agg_LonPM180 on NOAA CoastWatch ERDDAP; mean of every fifth day 1991-2020.
  28. For the Quang Ninh to Thanh Hoa coast (which includes Halong Bay), July, August and September together account for this share of storms and tropical depressions affecting the coast in 1961-2014, according to Vietnam's Institute of Meteorology, Hydrology and Climate Change 76%. Nguyen Van Thang et al., 'Ảnh hưởng của bão ở Việt Nam thời kỳ 1961-2014', VNU Journal of Science: Earth and Environmental Sciences 32(3S), 2016, 210-216.
  29. Storm suspensions on Halong Bay stop departure permits; they are issued by the Quang Ninh inland waterway port authority (Cảng vụ Đường thủy và Đăng kiểm phương tiện thủy nội địa, under the provincial Department of Construction) on the direction of the provincial disaster steering committee, or come as a notice of the provincial Department of Agriculture and Environment to that authority (Matmo 2025, Storm No.1 2026); the body that stops the permits is Quang Ninh Inland Waterway Port Authority. Ha Long Bay Management Board website, suspension notices 2025-2026 (posts 240, 268, 287, 292, 990, 1215), 3 July 2026.
  30. Since mid-2026 a real-time thunderstorm, squall and lightning warning service for Halong Bay and Bai Tu Long Bay, run with the Northern Region Hydro-Meteorological Station, splits the bays into nine warning zones and gives warnings about 10 to 15 minutes ahead; its address is https://halong.navy01.com/. Ha Long Bay Management Board website, post 1013 'Cảnh báo sớm dông lốc trên biển' (2026-07-11), citing Quang Ninh Department of Agriculture and Environment, 11 July 2026.
  31. Storm odds and weather by month. Storm tracks: NOAA NCEI IBTrACS v04r01, seasons 1991 to 2025, systems within 150 km to 350 km of Halong Bay; a stop counted as 2 days from the board notice to the final national bulletin. Weather: NOAA Global Summary of the Day, Phu Lien (Hai Phong) and Bach Long Vi, 1996 to 2024; sea surface temperature: NOAA OISST v2.1, the grid cell south of Cat Ba Island, 1991 to 2020. Stop log: Ha Long Bay Management Board notices and the national final storm bulletins (data/suspensions.json).

Photographs

  1. Halong Bay in mist or fog. Photo: aschaf / Wikimedia Commons, CC BY 2.0
  2. Bai Tu Long Bay seascape. Photo: Benjamin Smith / Wikimedia Commons, CC BY-SA 4.0
  3. Wide Halong Bay seascape with karst islands. Photo: Christophe95 / Wikimedia Commons, CC BY-SA 4.0
  4. Cat Ba town harbour. Photo: Christophe95 / Wikimedia Commons, CC BY-SA 4.0