Koh Samui in November: The One Month the Gulf Loses
Koh Samui in November is the Gulf coast's wettest month. What the rain really does, which ferries stop, and what the island is still good for.
Koh Samui in November is the wettest month the island gets, and it is the wrong month to book if the beach is the point. Published November rainfall figures range from about 295 millimetres to 445 millimetres across roughly 16 to 20 rain days. That spread is real, and I will come back to why it is so wide.
Last verified 14 October 2026. Every number on this page is a climate average from a named source. Weather is not a schedule, and no forecast for a monsoon season three months out is worth trusting.
I spent the third week of November 2024 on the west coast of Samui, in a bungalow at Mae Nam, and I want to be precise about what happened. It rained for two and a half days without a real gap. Then four days of heat and glare and a sea so flat I swam across the bay twice. Then it rained again.
That is the shape of the month. It is not forty days of grey. It is two or three long events with good weather in between, and nobody can tell you in September which weeks they will land on.
Why Samui's rainy season runs opposite to Phuket's
Thailand has two monsoon systems and they do not arrive on the same coast. The southwest monsoon crosses the Andaman from about May to October. The northeast monsoon reaches the Gulf from roughly November to February.
Samui sits on the Gulf side. So does Koh Phangan, Koh Tao, and the mainland towns of Surat Thani and Chumphon. The practical consequence is that the island's wet season is late, roughly mid-October to mid-December, and it peaks hard in November. Whereas Phuket, Krabi and Koh Lanta are drying out and hitting their best conditions in the same fortnight.
Two coasts, seven hundred kilometres apart, opposite weather in the same week. People get this wrong constantly, and it is the single most expensive planning mistake in a Thailand beach holiday.
The compensation arrives in the middle of the year. From May through September, when the Andaman is being rained on, Samui is usually having some of its better weather. February to April is the one window when both coasts are dry.
What the November rain on Samui looks like
November rain on the Gulf comes in systems. A trough parks over the lower Gulf and it rains for two, three, sometimes five days more or less continuously, sideways and grey, with swell that closes the east-coast beaches and keeps the small boats tied up.
That is a different animal from the afternoon downpour most people picture when they hear "tropical rainy season." The classic Thai rainy season elsewhere is a hard hour at four o'clock and a clear evening. What arrives here is a weather event with duration.
A typical November holds two or three of these. Between them you get good days, which is why the month is not a write-off. The problem is that a five-night trip can lose three days to one system, and you cannot schedule around something that has not formed yet.
October and December also carry heavy rain, and the three months together take roughly half the island's annual total. October sits somewhere between 234 and 310 millimetres depending on the source. December falls to about 150 to 210. Annual rainfall runs around 1,645 millimetres, against roughly 44 to 47 millimetres in the driest month, which is February or March.
Which ferries run in November and which stop
This is the part that catches people out, because the answer is not "all of them" or "none of them."
The big mainland crossings keep going. Seatran and Raja from Donsak, plus Lomprayah's Surat Thani and Chumphon routes, run through most of the monsoon and have kept sailing even during serious flooding years. Samui to Koh Phangan is a short hop and runs more often than it stops.
The exposed leg is the problem. Koh Tao is the long crossing, the catamarans are fast and light, and Lomprayah and Seatran will hold or cancel their Gulf island services to Koh Tao whenever the harbour master calls the sea unsafe.
That is not theoretical. Between 19 and 21 November 2025, operators including Lotus Ferry and Lomprayah suspended Surat Thani to Koh Tao and the return leg outright. Forecasts at the time called for more than 1,000 millimetres of accumulated rain over ten days, with three to five days of continuous day-and-night rain from 20 to 24 November, and another spell from 30 November into 2 December.
The Haad Rin longtails on Phangan pack up for the season earlier than the big operators do.
Flights are more reliable than the sea. Samui airport delays, and it rarely loses a whole day. Anyone crossing to Koh Tao should build slack into both ends and avoid booking a non-refundable onward flight for the morning after the crossing.
What still works, and what stops
| Status in November | |
|---|---|
| Mainland ferries from Donsak | Running most of the month |
| Samui to Koh Phangan | Usually running |
| Gulf island crossing to Koh Tao | Frequently held or cancelled |
| Ang Thong Marine Park | Closed to boats from early November to mid-December |
| Sail Rock and Chumphon Pinnacle diving | Frequently cancelled |
| Pools, spas, cooking courses | Unaffected |
| Hotel rates | Down 30 to 50 percent |
Ang Thong closing is worth planning around, because it is one of the best day trips in the country and it is simply not available. The Department of National Parks shuts the park to boats from the start of November until mid-December, every year without exception, so an early-November arrival will not see it at all.
Diving splits by site. Sail Rock sits exposed to the northeast and trips are cancelled often through November. Chumphon Pinnacle is the most exposed of the lot. Ang Thong, which sits west of Samui, is sheltered from the northeast monsoon and can still be diveable on days when Sail Rock is off. Operators run whatever the sea allows, and some of the calm days after a system passes produce exceptional diving, because the plankton that builds through the monsoon concentrates baitfish and the baitfish pull in predators.
Timing November, and when it turns
Late November is a different month from early November. The monsoon retreats through the second half, and the final ten days often deliver sunshine, calmer water and a genuine improvement, at prices still below the December peak. An arrival around the 20th and a departure in early December gets most of the benefit.
Some sources go further and claim rainfall peaks in October, with November improving week by week. Those pages tend to be selling accommodation. The weight of published climate data puts Samui's peak in November, and the multi-day storm events of recent years have landed in November too. Treat the optimistic version as a sales argument.
Smaller resorts close in November and early December. Ask before you book, because a closed restaurant and an empty bar make a quiet island feel abandoned.
Hotel rates are the month's one unambiguous advantage. Expect 30 to 50 percent off high-season pricing, with October and November the cheapest stretch of the year. A resort with a good pool and a spa becomes a rational choice in a way it never is in February.
What to do if your dates are already locked
Basing yourself on the west coast helps. Nathon, Mae Nam, Lipa Noi and Taling Ngam catch less of the northeast weather than Chaweng and Lamai on the east side, and the sea is calmer on that side more often.
Book refundable, or book nothing you cannot move. Watch the Thai Meteorological Department Gulf outlook as the date approaches, because a system shows up in the forecast days before it arrives. A November trip built on non-refundable advance bookings has no way to absorb a three-day system.
Consider the Andaman instead, and be honest about the trade. Phuket, Krabi, Koh Lanta and Koh Lipe are opening up through November and near their best by the second half. If the beach and the sea are the whole reason for the trip, that is the better coast.
Choose somewhere with a pool worth sitting beside. A cooking course, a spa week, a resort you would happily not leave, a long stay somewhere warm with a good book. Samui in November is perfectly good at all of that, at half price.
One warning on swimming: the Gulf does not carry the same year-round rip-current and drowning profile the Andaman has during its own monsoon, and the sea stays around 29 degrees all year. That does not make a red-flagged beach safe. If the flags are out, stay out.
The month-by-month guide covers how the two coasts compare across the whole year, and the Gulf storm season explains where November sits in the bigger pattern.
Frequently asked questions
Is Koh Samui in November worth visiting?
For a resort, spa or cooking holiday at roughly half price, yes, provided you accept that a multi-day system could take three days of it. For a beach and sea holiday, no. The east-coast beaches are often red-flagged and the Gulf is at its roughest. Switch to the Andaman coast for that trip.
How much does it rain in November on Koh Samui?
Published figures disagree, which is why I have given a range. November rainfall is quoted at anywhere from about 295 to 445 millimetres over roughly 16 to 20 rain days. The mean monthly figure most often cited sits near 300 millimetres, and the highest is used by diving and travel sites. The event pattern matters more than the total.
Do ferries to Koh Phangan and Koh Tao get cancelled?
Mainland ferries from Donsak rarely stop, and the Samui to Phangan hop usually runs. The Koh Tao crossing is the exposed one, held or cancelled whenever the harbour master calls rough seas. That is not hypothetical: from 19 to 21 November 2025, several operators suspended the route outright, as Pattaya Mail reported at the time.
When does Koh Samui's rainy season end?
The monsoon retreats through the second half of November, and the last ten days of the month often turn pleasant, with prices still below the December peak. The first half of December stays unsettled, and reliable high-season weather settles in from around the middle of the month.
Is February a better month than November?
By a distance, yes. February and March are the driest months, at roughly 44 to 47 millimetres of rain, with calm seas and about eight hours of sunshine a day. February to April is also the one window when both the Gulf and the Andaman coasts are dry at the same time.
The version I would give a friend
A bad beach month and a good value month, and the two facts turn out to be the same fact. The island does not shut, the mainland boats keep running, and half the days are pleasant.
Two things decide whether you enjoy it. Whether you can move your dates if a system parks itself over the Gulf, and whether your accommodation has a pool worth sitting beside. Lock those down and you get a quiet, cheap, green island with good food and nobody in the restaurants.
Book it for the beach instead, and you will spend the week watching a flag. Have a look at Koh Lanta, Phangan and Tao compared for a sense of which Gulf island suits which trip, and read up on the Full Moon Party if Phangan is on your route, since those dates run on the lunar calendar and not the monsoon one.
Sources for this post: published Koh Samui climate averages from weather-and-climate.com and the Thailand meteorological summaries cited by travel and dive operators, the Pattaya Mail report of the 19 to 21 November 2025 Surat Thani to Koh Tao suspensions, Thai national park guidance on the Ang Thong closure, and the Department of National Parks season dates for the Gulf islands.
