- The best time to visit Ang Thong is January to September, when the sea is usually calm and the water clearest.
- February to April is the driest and most reliable stretch for a smooth crossing, but also the hottest and one of the busiest.
- October and the second half of December are the rainy season: tours run, but on rough days the captain may change the route or cancel.
- The park is usually closed every year from 1 November to 15 December, and no tours run then.
- In the rainy months the big boat and the Red Baron are smoother than any speedboat.
You have a week on Koh Samui booked for next year, and one day of it is going to Ang Thong. The question is which week, because the same 40-minute crossing can be a glassy ride or a bumpy one depending on the month. The best time to visit Ang Thong is easy to name in one line, but the details decide if your day is good or great.
Here is how the year really looks from Samui, month by month, from someone who checks the sea every morning.
When is the best time to visit Ang Thong?
The best time to visit Ang Thong is January to September, when the sea is usually calm and the water clear. If I had to pick the most reliable months for a smooth crossing, I would choose February, March and April.
Koh Samui has a different weather pattern from Phuket and the Andaman coast. Its main rainy season comes late in the year, roughly October to December, and the national park closes for part of it. That leaves a long, open window from the New Year through September.
The air is warm all year, with an average around 28 °C, so temperature is never the problem. What changes is the sea, the rain and the number of people on the boats.
If you want the quick version before the details, these are my picks:
- Calmest crossing: February to April.
- Best value and fewer people: May and June.
- Good for family holidays: July and August, with busier boats.
- Last calm month: September, ideally the first half.
- Go only with a flexible plan: October and the second half of December.
Rain itself is rarely the deal-breaker. A warm shower on a beach in Ang Thong is no hardship. Wind is what matters, because wind makes waves, and waves decide how the crossing feels and whether the reef is clear.
Ang Thong month by month: sea, rain and crowds
This table sums up a typical year. Weather never follows a calendar exactly, so read it as the odds, not a promise.
| Month | Sea | Rain | Crowds | My verdict |
|---|---|---|---|---|
| January | Usually calm, can still be breezy early | Rain fading | Busy | Good |
| February | Calm | Dry | Busy | Excellent |
| March | Calm, clear water | Dry | Busy | Excellent |
| April | Calm, clear water | Dry, very hot | Busy around Thai New Year | Excellent, start early |
| May | Usually calm | Short showers possible | Quieter | Very good value |
| June | Usually calm | Short showers possible | Quieter | Very good |
| July | Usually calm | Short showers possible | Busy (school holidays) | Good |
| August | Usually calm | Short showers possible | Busy (school holidays) | Good |
| September | Usually calm | Showers more frequent | Quiet | Good, a little more risk |
| October | Rough days more common | Rainy season | Quiet | Risky, choose a stable boat |
| 1 Nov to 15 Dec | Park usually closed | Peak rains | No tours | Not possible |
| Late December | Rough days possible after reopening | Still rainy season | Very busy (holidays) | Risky, book flexibly |
The crowd column is about Koh Samui as a whole. On busy weeks the group boats are fuller and the popular stops more crowded; on quiet weeks you notice the space.
January to April: the dry season and the calmest crossing
From late January to April you have the best odds of flat water, dry skies and clear visibility. This is the classic high season, and for good reason: all tours run on schedule, and it is worth booking a few days ahead.
January can start with a bit of leftover wind and the odd shower from the rainy season, especially in the first days of the month. By February the pattern usually settles, and March and April are the months I recommend most to people who worry about seasickness.
The catch is heat. April is the hottest month on Samui, and the climbs in Ang Thong are steep: the stairway to the Emerald Lake is short, but the trail on Wua Ta Lap is about 500 meters and hard work at midday. Take more water than you think you need. If you are unsure about the climb, read how hard the Wua Ta Lap viewpoint hike is before you go.
Crowds are the other trade-off. High season means fuller boats. If that bothers you, a small-group tour or a weekday booking helps more than changing the month.
May to September: calm water and better value
May to September is still a good time for Ang Thong, and in my opinion underrated. The sea is usually calm, the water clear, and short showers are possible but tours run normally.
Koh Samui does not get the heavy summer monsoon of Phuket, so this stretch is often pleasant. Expect a passing shower now and then, usually short. Clouds also keep the viewpoints a little cooler than in April.
May and June are my value picks: fewer visitors than the high season and generally good conditions. July and August are busier again with European and family holidays, but the sea is usually still fine. September is the last of the calm months; showers become more frequent towards the end, so I would put a September trip in the first half of your stay to keep a spare day.
Summer is also a lovely time for nature. The rare Ang Thong lady's slipper orchid flowers from April to August, and dusky langurs are around the park headquarters all year. For more on the animals, see the Ang Thong wildlife guide.
Is October a good time to visit Ang Thong?
October is the riskiest open month. It is the start of the rainy season on Samui, rough days become more common, and on bad days the captain may change the route or cancel.
That does not mean every October day is bad. Many are perfectly fine, with sunshine between showers. But visibility for snorkeling drops after heavy rain or strong wind, and kayaking can be shortened or cancelled when the sea is up.
If October is your only option, two things help. First, choose a stable boat: the big boat tour or the Red Baron are smoother than speedboats when there is swell. Second, book early in your stay so there is room to move the date if the weather turns.
There is an upside, too. October is one of the quietest months on Samui, so on a good day the boats are less full and the beaches emptier. Some of my favourite Ang Thong days have been on a clear October morning after a night of rain, with the islands washed green. You just have to accept that it is a gamble.
The same advice applies to the second half of December. The park usually reopens around 15 December, but it is still the rainy season, and the Christmas and New Year weeks are among the busiest of the year on Koh Samui.
1 November to 15 December: the park is closed
The national park is usually closed every year from 1 November to 15 December to let nature recover. No tours run, no park tickets are sold, and these dates cannot be booked.
The exact dates are announced by the Department of National Parks each year, so if you are planning a trip around the reopening, check with the booking team before you commit. Closure details get their own article soon.
If you are on Samui during the closure, there is no way around it: no tour or private boat can take you in. Plan Ang Thong for another trip, or come in the second half of December and keep your date flexible.
Which tour suits which season?
In the calm months every tour works, so choose by budget and style. In the rough months, choose the most stable boat you can.
- February to April: any tour. The speedboat (฿1890) gives the most time on the islands; the VIP speedboat (฿3890, park fee included) avoids the high-season crowds with a maximum of 16 guests.
- May to September: the speedboat is the best balance, and kayaking is at its best on calm water. See the guide to kayaking in Ang Thong for where you paddle on each tour.
- October and late December: the big boat (from ฿1100) or the Red Baron (฿3700, park fee included). Both ride the waves far better than a speedboat.
- Any month, your own plan: the private speedboat (฿39,000 for up to 6 guests) lets you choose the day and time, but it is still a speedboat on rough water.
Pick the speedboat for a classic day in the calm months, the VIP for a quieter high-season trip, and the big boat or Red Baron if you are travelling in the rainy season or prone to seasickness.
- Days
- Daily
- Time
- 07:40-16:30
- Boat
- Shared speedboat
- Park fee
- ฿300 extra
- Days
- Tue, Thu, Sat
- Time
- 07:00-17:30
- Boat
- Small group, max 16
- Park fee
- Included
- Days
- Daily
- Time
- 07:30-17:00
- Boat
- Large tourist boat
- Park fee
- ฿300 extra
- Days
- Wed, Sat
- Time
- 07:30-19:00
- Boat
- Traditional sailing junk
- Park fee
- Included
Practical tips for choosing your date
Whatever the month, a little flexibility makes the biggest difference. These are the habits I recommend to friends:
- Book Ang Thong for the first half of your stay, so a weather cancellation can be moved to another day.
- Check the wind forecast the evening before. A calm forecast matters more than a few clouds.
- Remember the VIP tour runs only on Tuesday, Thursday and Saturday, and the Red Baron on Wednesday and Saturday.
- If the tour company cancels for weather, you get a new date or a full refund including the card fee. The rules for your own cancellations are in the cancellation policy.
- In April, bring extra water and shoes with grip for the climbs.
- In the rainy months, pack a waterproof phone pouch and a light layer for the ride home.
Questions and answers
What is the worst month to visit Ang Thong?
November, because the park is usually closed from 1 November to 15 December and no tours run. Among the open months, October has the highest chance of rough sea.
Is Ang Thong worth visiting in the rainy season?
It can be, as long as you avoid the annual closure. In October and late December tours still run, but the captain may change the route or cancel on rough days, so keep your date flexible and choose a stable boat.
When is the water clearest for snorkeling in Ang Thong?
From January to September, when the sea is calm. After heavy rain or strong wind the water can turn cloudy.
Is Ang Thong open at Christmas?
The park usually reopens around 15 December, so tours normally run over Christmas and New Year. It is still the rainy season and a very busy time on Samui, so book early and keep a spare day.
Is it too hot to visit Ang Thong in April?
It is hot, but the trip is very doable. Drink plenty of water, wear a hat and take the climbs slowly; you can always stay on the beach instead of hiking to the top viewpoint.
Do the tours run every day in high season?
The speedboat and the big boat run daily while the park is open. The VIP speedboat runs on Tuesday, Thursday and Saturday, and the Red Baron on Wednesday and Saturday.
How far ahead should I book in high season?
A few days ahead is usually enough for the daily tours. For the VIP speedboat or the Red Baron, which run only on certain days, book earlier if you need a specific date.
Facts checked against our tour pages on 2 November 2026. Prices and days can change: your manager confirms them when you book.
