Trip Handbook Vietnam

Seasonal Hazards & Natural Dangers in Vietnam

Vietnam's weather is three countries in one: the north, the centre and the south run on different calendars. The month that floods Hoi An is the best month in Hanoi, and the month that cancels Ha Long Bay cruises is beach season in Da Nang. This page is the calendar version of that — when each danger peaks, what it actually does to your trip, and what to do about it.

Patterns, not forecasts. Everything below is a long-term pattern — the month a danger usually peaks. Single years vary widely: November 2025 brought record floods to the centre and south that no average predicted. Always check the live forecast a few days before you travel (see Where to check).

When each danger peaks — by region and month

HazardJanFebMarAprMayJunJulAugSepOctNovDec
Typhoons — North (Hanoi, Ha Long, Sa Pa, Ninh Binh)◐●●●●◐
Typhoons — Central coast (Hue, Da Nang, Hoi An, Phong Nha)◐●●◐
Typhoons — South-central coast (Nha Trang)◐●●◐
Flooding — Hoi An & Hue old towns◐●●◐
Flooding — Ho Chi Minh City streets (rain + king tides)●●◐
Landslides — Sa Pa mountain roads◐●●◐
Landslides — Da Lat passes (after prolonged rain)◐◐◐◐◐◐◐
Cave closures — Phong Nha●●●◐
Rough seas — Phu Quoc boats & ferries◐●●●●◐
Cruise suspensions — Ha Long Bay◐●●●◐
Fog / low visibility — Ha Long Bay●●◐
Cold & fog — Sa Pa●●●
Extreme heat — lowlands nationwide●●◐◐◐

● peak danger   ◐ possible   blank = low. Da Lat's November mark is for prolonged rain generally — the November 2025 pass closures were exceptional, not a yearly pattern.

Typhoons & tropical storms

Vietnam's storm season runs roughly from June to the end of November, and it moves from north to south. The north takes its typhoons from June to August; the central coast from early October to mid-November; the south-central coast (Nha Trang) from October to December, with November the highest-risk month. On the long-term average, the East Sea sees about 9.6 storms between August and December, and about 3.8 of them directly affect Vietnam's mainland.

What it does to a trip: cruises stop, flights move, mountain roads close for landslides rather than wind. Super Typhoon Yagi made landfall in Quang Ninh on 7 September 2024 with winds over 200 km/h — the strongest typhoon to hit Vietnamese land in 70 years — and Ha Long Bay cruises stopped entirely while it approached. 2025 brought 20 storms and depressions, the most in 30 years.

What to do: build one or two slack days into any trip that includes Ha Long Bay or an island in storm season, and book cruises and island tours with free cancellation. Check the forecast three to five days before you travel — storms are forecast days ahead, and the country handles them competently: evacuations happen, cruises stop, flights get moved.

Flooding in towns

Hoi An's Ancient Town floods in most years in October and November, when the Thu Bon River rises after sustained rain. Most floods are shallow and brief — knee-deep water on the lowest riverside streets for one to three days. Exceptional years have seen water approaching two metres (1964, 1999, 2007, 2017, 2020), and in October 2025 the river peaked 14 cm above its 1964 mark. October averages about 628 mm of rain, November about 448 mm.

Hue floods too: in October and November the Perfume River can rise by several metres, with the south bank flooding first. In Ho Chi Minh City the problem is rain plus tide: streets flood most often in September and October, when heavy rain meets the year's highest tides in the Saigon River — water can rise to ankle height or more within minutes. In November 2025 the Phu An tide gauge set an all-time high of 1.78 m, and central streets including Bui Vien went under water. In Nha Trang, days of rain in mid-November 2025 flooded low-lying districts, with water over two metres in places.

What to do: in October and November, stay a little away from the river in Hoi An, keep your plans flexible, and check conditions with your hotel before you go out. Never wade or drive through floodwater — you cannot see what is under it. In Ho Chi Minh City, allow extra time for journeys around high tide in October and November, and avoid ground-floor rooms in low-lying areas.

Landslides & mountain roads

Heavy rain, not wind, is what closes mountain roads. In Sa Pa, July and August each average over 400 mm of rain, and landslides and flash floods can close the roads in and out of town — a rockfall blocked National Highway 4D at Ta Phin for several hours in May 2026.

Da Lat's passes are the same story on a bigger scale. In November 2025, exceptional rains cut every main route into the city at once: a collapse at Mimosa Pass tore a 50-metre-wide, 30-metre-deep chasm in the road, Prenn Pass and National Highway 20 closed too, and the province declared a state of emergency. Prenn Pass reopened on 25 November with trucks still banned. That November was exceptional, not a yearly pattern — but it shows why you check road conditions before any mountain drive.

The Hai Van Pass between Hue and Da Nang is foggy in rain and carries a landslide risk after heavy rain; the city warned visitors off it, Son Tra and the Ba Na Hills road during the October 2026 storms. The Khanh Le Pass between Nha Trang and Da Lat was hit by landslides in November 2025.

What to do: do not drive a mountain pass in or just after heavy rain, at night, or in dense fog. Ask your hotel or driver about road conditions that morning. On the Hue–Da Nang route, cars and buses can use the Hai Van Tunnel instead of the pass road (motorbikes cannot use the tunnel).

Caves that flood — Phong Nha

Phong Nha's rainy season runs from roughly mid-September to mid-December, and it is the one window worth avoiding if the caves are the point of your trip. Paradise Cave is dry and high above the valley floor, so it stays open through almost everything. Phong Nha Cave closes when the Son River rises past the jetty — typically for two to five days at a time. The Dark Cave zipline and mud bath are reduced or closed from mid-September, Mooc Spring is often closed in October and November, and river caves and swim-through tours are suspended from mid-September to mid-November.

The big expeditions run on fixed seasons: Son Doong from January to August only, Hang En from December to mid-September. In late October 2024, Storm Trami put enough water into the province that the authorities suspended all cave tours, forest expeditions and water activities in the park at once.

What to do: book cave trips between February and August. If your dates fall in September to December, check with your operator the week before you travel — closures are announced day by day, not for the season.

Rough seas & boat cancellations

From May to October the south-west monsoon brings heavy rain and rough seas to Phu Quoc's west coast. Island-hopping and snorkelling tours — and the ferries to the mainland — are cancelled when the sea is too rough, most often from June to September. The east and south coasts (Bai Sao, Bai Khem) are more sheltered in those months. Do not put a ferry crossing on the day before an international flight.

In July 2026 a tourist speedboat capsized in rough seas off Hon May Rut and 15 passengers died; the authorities then suspended speedboats without the certificate needed to carry passengers. Book with an established operator, wear the life jacket, and do not go out in rough weather.

On the south-central coast, sea bans run from September to November: in November 2025 the province banned boats from leaving port for Typhoon Kalmaegi and more than 300 tourist vessels were halted in Nha Trang. In Ha Long Bay, the port authority stops issuing departure permits on a storm warning — see Typhoons above.

What to do: put boat days early in your trip, not on the last day, and book with free cancellation.

Fog & low visibility

February and March bring the worst visibility of the year in Ha Long Bay — about 1.5 hours of sunshine a day, persistent low cloud and drizzle, and fog that can drop visibility under 100 metres. The port authority suspends departures when fog falls below a safe level, so fog can delay or cancel a cruise just like a storm. If seeing the bay clearly matters to you, treat February and early March as months to avoid.

In Sa Pa, fog can sit over the valley for days at a time from December to February, hiding the terraces and the mountains completely.

Cold in the mountains

Sa Pa sits at about 1,500 metres, and winter there is properly cold: average lows of 6–8°C from December to February, cold snaps that push nights close to freezing, and frost on the coldest mornings. Snow is rare in town but falls occasionally on Fansipan (3,143 m), which is cold and windy even in summer. Pack a warm layer and a rain jacket even in summer — the weather can turn in minutes.

Extreme heat

April and May bring the year's worst heat. In early April 2026, temperatures in the north-central corridor reached about 40°C, with 41.9°C recorded in Nghe An, and the national forecaster issued heat warnings across the centre. Vietnam's all-time record is 44.2°C, set in Nghe An in May 2023. From May to August the lowlands regularly pass 35–38°C at midday.

What to do: drink water constantly, plan the midday hours in shade or indoors, and do not climb exposed hills (like Hang Mua in Ninh Binh) in the midday heat. Heatstroke is a real risk for hikers — headache, nausea and confusion mean stop, shade and water, then medical help.

What to do

Before you book

Build one or two slack days into any trip that includes a cruise, an island or a mountain pass in storm season. Book with free cancellation where it is offered. Buy travel insurance that covers weather delays and cancellations — and read the wording, because “bad weather” is not covered by every policy.

Before you go

Check the forecast three to five days out, and again the day before. See Where to check below.

When a storm is coming

Follow the local authorities, not your itinerary. When the port authority suspends sailings, no operator can override it — and you should not pressure one to try. If your hotel or guide says a road or a cave is closed, believe them.

In an emergency, call 113 (police), 114 (fire and rescue) or 115 (ambulance) — see the Safety & SOS page for hospitals and tourist police numbers.

Where to check

Sources

Checked 7 November 2026. Rainfall figures are long-term averages; single years vary widely.