Koh Samui in November surprises a lot of visitors. While Phuket and the Andaman coast are drying out, Samui, on the Gulf of Thailand side, is in the thick of its rainy season. That does not rule November out. It does change how you plan, especially if a boat trip is high on your list.
| Quick answer | November is Koh Samui’s wettest month, averaging about 445 mm of rain on 16–17 days, with highs of around 30°C. The north-east monsoon makes the sea rough on some days. Boat trips to the southern islands still run when conditions are safe, but Ang Thong Marine Park is closed from 1 November to 15 December 2026. |
| Average temperatures | High 29.7°C, low 24.1°C (1991–2020) |
| Best approach | Flexible dates, a boat day early in your stay and a land plan for rough days |
Koh Samui in November: the weather in numbers
The figures below are the World Meteorological Organization’s 30-year averages for the Ko Samui weather station (WMO climate normals, 1991–2020). February, the island’s driest month, is there for comparison.
| Month | Avg high | Avg low | Rainfall | Days with 1 mm+ rain |
|---|---|---|---|---|
| October | 30.6°C | 24.3°C | 295 mm | 15.8 |
| November | 29.7°C | 24.1°C | 445 mm | 16.5 |
| December | 29.3°C | 24.0°C | 263 mm | 11.6 |
| February | 29.4°C | 24.9°C | 64 mm | 4.3 |
It stays warm. Average highs are only a degree or so below the yearly figure, and nights rarely feel cool. The rain is the big difference. November gets roughly seven times as much as February, and some of it falls in long, heavy spells rather than short tropical showers.
Averages are not forecasts. On average, nearly half the days in November get less than 1 mm of rain, and some years are drier than others. In November 2025, the Thai Meteorological Department recorded rainfall on southern Thailand’s east coast at 91% of normal. Late that month, though, torrential rain caused serious flooding further south in Songkhla province.
Why November is wet on Samui (but not in Phuket)
Thailand has two monsoons. The south-west monsoon, roughly mid-May to mid-October, brings the Andaman coast its rainy season. The north-east monsoon takes over from around October and blows across the Gulf of Thailand, bringing its heaviest rain to the Gulf coast of southern Thailand, Samui included.
The Thai Meteorological Department’s November 2025 summary shows the pattern. The north-east monsoon covered the Gulf of Thailand, the south and the Andaman Sea for almost the whole month and became rather strong towards the end. On Samui, a stronger monsoon means more wind from the north-east, more waves in the Gulf and a higher chance that your boat trip gets postponed.
Sea conditions: what it means for boat trips
For a day at sea, wind and waves matter more than rain. A grey, still day can be pleasant on the water, while a bright, windy one can be uncomfortable or unsafe. This is how it plays out in November.
- Decisions are made day by day. Responsible operators check the forecast and sea state shortly before each departure and postpone if it is not safe.
- Shorter crossings fare better. Trips that hop between islands close to Samui’s south coast cross less open water than longer routes further offshore.
- Boat size and type matter. Small, fast boats feel choppy water much more than larger ones. If you get seasick, pick a larger, steadier boat on a short route.
- Visibility for snorkelling can drop. Rain run-off and stirred-up sediment can make the water less clear than in the calmer months.
Which trips still run in November
| Trip | November status | What to know |
|---|---|---|
| Ang Thong National Marine Park | Closed 1 November–15 December 2026 | Annual closure under the DNP’s official 2026 list. Due to reopen on 16 December |
| Five Islands, Koh Tan and Pig Island by catamaran | Runs when it is safe | Short hops along the south coast, postponed if the sea is unsafe |
| Speedboat or longtail trips from Thong Krut | Runs when it is safe | Smaller boats are more affected by wind and waves |
| 4×4 island tours | Land-based, so the sea is not a factor | Heavy rain can still make it a wet day. Check the itinerary on the day |
| Elephant sanctuary visits | Land-based, so the sea is not a factor | Wear clothes you do not mind getting muddy |
Choosing between the two main island days? See our Ang Thong or Pig Island comparison, and bear in mind that only one of them is open in November.
The 1-Day Catamaran in November
The Samui Journey catamaran leaves from Bang Kao Pier and visits the Five Islands, Koh Tan for snorkelling and Pig Island (Koh Madsum). Hotel pickup is between about 9:00 and 9:40 AM, depending on your hotel area, and you are back at your hotel at around 4:30 PM. The captain is licensed with more than 10 years’ experience, and everyone gets a life jacket.
This month, the weather policy matters most. If the sea is not safe, your trip moves to a new date first. If bad weather hits the new date as well, you get a full refund. The boat also needs at least 40 guests to sail. If it does not reach that number, you can choose a new date or a full refund.
Land days
- Explore the Real Samui 4×4 Island Safari. From ฿1,950 per adult and ฿1,650 per child aged 5–11, and under-5s go free.
- Samui Elephant Kingdom. ฿3,000 per adult and ฿1,700 per child aged 5–11, and under-5s go free. It is a sanctuary that Samui Journey supports and books visits to, but does not own.
For indoor and covered options on the wettest days, see our rainy-day guide to Koh Samui.
How to plan a November holiday on Samui
- Put the boat day early in your stay. If it is postponed, you still have days left to try again.
- Keep two or three flexible days. Move your land and sea days around the forecast instead of fixing them in advance.
- Book with clear policies. Check the weather rule, the minimum group size and the cancellation deadline. With Samui Journey, cancellation is free up to 24 hours before pickup. Later cancellations and no-shows are non-refundable.
- Watch the marine forecast more than the rain icon. Wind strength and wave warnings tell you more about a boat day than the chance of a shower.
- Pack for wet and sun. Bring a light rain jacket, a dry bag and quick-dry clothes, plus sunscreen, because the sun is strong between showers. Our boat day packing checklist covers the rest.
- Ask before you book. If you are unsure about a date, message the operator. A good one will give you a straight answer on how the sea is looking.
Is November a good time to visit Koh Samui?
It is if you are flexible. November works for people who are happy to read, swim at the hotel or head inland when it rains, and who treat a sunny boat day as a bonus, not a guarantee. It is harder on a short stay with a fixed list of sea trips, or if you are set on Ang Thong.
If you can move your dates, compare November with the drier months in our month-by-month guide to the best time to visit Koh Samui. February to April is the most reliable stretch for calm seas.
Visiting in November? Pick a date and we will tell you plainly how it looks.
The 1-Day Catamaran to the Five Islands, Koh Tan and Pig Island includes lunch, drinks, accident insurance and hotel transfers. Adults ฿3,300, children (5–11) ฿1,900, under-5s free. Bad weather means a new date first, with a full refund if that date is also cancelled. See the 1-Day Catamaran or message us on WhatsApp at +66 94 751 4988.
FAQ
Does it rain every day in Koh Samui in November?
No. On WMO averages, November has about 16–17 days with at least 1 mm of rain, so nearly half the days are dry or almost dry. When it rains, though, it can be heavy and last for hours.
Is the sea rough around Samui in November?
Often, yes. The north-east monsoon blows across the Gulf of Thailand, and some days are too rough for boat trips. Other days are calm enough to sail, so decisions are made day by day.
Can you go to Pig Island in November?
Yes, on days when it is safe to sail. Pig Island is outside Ang Thong National Park, so the November closure does not apply to it.
Is Ang Thong open in November?
No. For 2026, Ang Thong National Marine Park is closed from 1 November to 15 December under the Department of National Parks’ annual closure list.
How hot does Samui get in November?
Warm. Average highs are about 29.7°C and average lows about 24.1°C.
What happens if my catamaran trip is cancelled in November?
With Samui Journey, the trip moves to a new date first. If bad weather cancels that date too, you get a full refund.
Plan your trip