Vietnam's Islands: The Best Months for Phu Quoc, Con Dao, Ly Son, Nha Trang and Co To

Thời Tiết editorial team Updated 8/1/2026

Why every stretch of coast keeps its own calendar

Vietnam's coastline runs through three distinct climate zones, so there is no single "beach season" for the whole country. In the same June week, Co To in the Gulf of Tonkin can be sunny and glassy while Phu Quoc's west coast is being soaked by the southwest monsoon. Two alternating wind systems explain it: the northeast monsoon, strongest from roughly October to March, and the southwest monsoon, which takes over from about May to October. Each region catches these winds differently, and typhoon season migrates from north to south through the year, leaving the three regions on almost opposite schedules.

Once you see this pattern, contradictory travel advice makes sense — people are simply talking about different seas.

Gulf of Tonkin: Co To's short but brilliant summer

Islands in the Gulf of Tonkin — Co To, Quan Lan, Cat Ba — feel the northeast monsoon most sharply. From about October to March, surges of cold air push down from the continent, whipping up strong offshore winds and days of rough sea. Ferries are frequently delayed or suspended when ports close, skies stay grey, and the water is cold.

Co To's window runs from late April to August: clear water, steady sunshine, far calmer crossings. The catch is that mid-to-late summer overlaps with the north's typhoon season, so a July or August trip needs a close eye on storm bulletins in the days before departure. If a system is heading toward the gulf, reschedule early — a port closure can strand you on the island for days.

Central coast: Ly Son and Nha Trang run on a late clock

The central coast is the odd one out: its rainy season arrives late, roughly September through December, exactly when much of the country is drying out. Those months are also the region's typhoon peak, bringing long spells of heavy seas.

For Ly Son, the comfortable stretch runs from about March to August, when the sea is calm and boats from the mainland run reliably every day. From September onward, swells build, sailings get cancelled at short notice, and the island can be cut off for days at a time.

Nha Trang enjoys a longer dry season, from about January to August, with March through August prime for swimming, snorkelling and island-hopping in the bay. October and November are typically the wettest months, sometimes with days of rain and rough water in a row. Before you go, check the Khanh Hoa weather forecast to line your trip up with a dry, low-swell stretch.

The south: Phu Quoc, Con Dao and the "gio chuong" wind

The southern seas have no real winter — just a dry season and a wet one. Phu Quoc is at its best in the dry months, roughly November to April: blue skies, light winds, and the west coast — home to most of the main beaches — as calm as a lake. From May to October the southwest monsoon blows straight onto that west coast, bringing more rain and noticeably bigger surf; if you travel then, favour the sheltered beaches on the east side. Keeping an eye on the Kien Giang forecast in the week before you fly helps you plan your beach days.

Con Dao, sitting far offshore, feels both monsoons in full. From about October to February, the "gio chuong" — the southern name for the northeast monsoon — churns the surrounding waters, and mainland ferries are often cancelled. The wet season from May to October brings swell from the southwest instead. That leaves roughly March to May as the sweet spot: calm water on both sides, sunshine, little rain. If you get seasick or travel with small children, consider flying rather than sailing in the windy months.

Monsoons and typhoons in one minute

Northeast monsoon (about Oct–Mar): rough seas in the Gulf of Tonkin and along the central coast; reaching the south it becomes the gio chuong, kicking up waves around Con Dao and the Mekong estuaries.
Southwest monsoon (about May–Oct): rain and surf for southwest-facing shores like Phu Quoc's, while the north and centre enjoy their sunniest season.
Typhoon season: migrates southward — roughly June to September for the north, September to November for the central coast, with the far south rarely, but not never, affected.

How to read wind and waves before booking

A few habits prevent most island-trip headaches:

Check the wind forecast, not just the rain. For passenger boats, wind decides everything: once it reaches roughly force 6, ports commonly suspend departures. A rain-free day can still mean a cancelled sailing.
Watch the forecast for three to five days before departure — accuracy improves sharply near the date. If a tropical depression forms, start planning a backup date.
Mind the wave height. Under 1 metre is comfortable; 1.5–2 metres will test anyone prone to seasickness and may hold smaller boats in port; above 2 metres, expect closures.
Book flexible tickets in the shoulder months, and avoid tight connections: never plan to step off a ferry straight onto a flight.
Take the earliest sailing — wind and chop build through the afternoon, so morning boats ride smoother and cancel less.
Keep a buffer day at the end in case the sea turns.