Koh Samui weather August is the best of the summer months on rainfall: on 30-year averages it gets less rain than any month from May to September. Showers still fall on about 14 days, but they are usually short, and the east coast is often calm.
This guide gives you the official averages, explains where to swim, and shows how to plan day trips to the neighbouring islands in August.
Koh Samui Weather August at a Glance
August is green-season summer with relatively low rainfall. Westerly winds keep the east coast calm on most days, and boat trips usually run.
- Rainfall
- 102.2 mm
- Rainy days
- 14.5
- Average high
- 32.4°C
- Average low
- 25.1°C
- Humidity
- 78%
- Wind
- 2.7 kn, west
These Koh Samui weather August figures are the 1991–2020 climate normals of the Thai Meteorological Department for its Ko Samui station. They describe a typical August, not a forecast for your dates, and one station stands for the whole island.
Good for
- Family summer holidays
- Day trips to Koh Phangan and Koh Tao
- East-coast beach holidays
- Travellers avoiding the Andaman monsoon
Think twice if
- You want guaranteed dry days
- You are sensitive to heat
- You are booking late for family rooms
- Your plans depend on the west coast sea
Where Koh Samui weather August sits in the year: average rainfall per month in millimetres, Thai Meteorological Department, Ko Samui station, 1991–2020. Select a month to open its guide.
August is busy with families
Compare what is still available for your dates and check each rate's cancellation terms.
Koh Samui Weather August: Rain and Heat
The Thai Meteorological Department's Ko Samui station records an average of 102.2 mm of rain in August over 14.5 rainy days. That is the lowest rainfall of the May to September period, although the number of rainy days stays similar.
The average high is 32.4°C and the low 25.1°C, with humidity around 78%. Cloud cover is at its highest of the year in August on the station's records, which takes a little of the edge off the sun.
Expect showers rather than long rain, and plan mornings for the beach.
Koh Samui Weather August: Sea Conditions and Swimming
Winds come mostly from the west in August, averaging 2.7 knots at the Ko Samui station. The east coast is usually the calmest for swimming, and the west coast can be choppy on breezy days.
Boat trips and ferries to the neighbouring islands usually run. After a squall, operators may postpone for a day.
Swimming safety
Lifeguard cover is limited on many Samui beaches. Stay out of the water when red flags are up or when waves break hard on the shore, keep children within reach, and ask your hotel about currents on the day. A calm-looking bay can still pull.
Koh Samui Weather August: Where to Stay
The east and north-east coasts are the easy choice in August for calm water. Families often pick Choeng Mon or Bophut for the mix of calm beach and walkable restaurants.
| Area | Coast | In August |
|---|---|---|
| Chaweng | East | Calm sea most days, everything on foot. |
| Choeng Mon | North-east | Sheltered and family-friendly. |
| Bophut and Bangrak | North | Close to piers for island trips. |
| Lamai | East | Calm water, relaxed. |
| West coast | West | Quiet and scenic; can be choppy. |
If you plan island day trips, a base near the north-coast piers saves time in the morning. Compare every area in our where to stay in Koh Samui guide.
When you have narrowed it down, compare rooms for your exact dates on Agoda and read the cancellation terms of each rate before you pay: they differ from one offer to the next.
Koh Samui Weather August: Best Things to Do
August is a good month for day trips to the neighbouring islands, as long as you watch the forecast.
| Activity | In August | Plan B |
|---|---|---|
| Koh Tao and Koh Nang Yuan | Usually running | Pig Island or Ang Thong |
| Ang Thong Marine Park | Open; usually running | Rebook after a squall |
| Koh Phangan day trip | Usually smooth crossing | Beach day on Samui |
| Snorkelling | Good on calm days | East-coast spots |
| Temples, viewpoints | Hot by late morning | Go early |
Plan sea trips for the morning and early in your stay.
Choosing the right boat
For long crossings, larger boats are more comfortable than small speedboats. For families with young children, a short trip to Pig Island or the islands off the south coast is easier than a full day at sea.
Sun and cloud
August is one of the cloudiest months on the station's records, but the tropical sun still burns through cloud. Keep sunscreen on even on grey days.
A day on Koh Phangan
Koh Phangan is close enough for a relaxed day trip from Samui's north coast. Thong Sala, the main port, has a weekend market, and beaches on the west coast of Phangan are usually calm with the westerly winds of August. Our Koh Phangan guide covers what to see.
Families in August
August is the busiest month for European families. Calm east-coast beaches, short boat trips and resort kids' clubs make it easy, but book early: family rooms, connecting rooms and villas are the first to sell out.
Afternoon showers and how to use them
Most August showers arrive in the afternoon and pass within an hour or two. Plan an indoor activity for that window, such as a massage, a cooking class or a long lunch, and use rain radar to time your next outing.
What to expect at night
Evenings are warm, with average lows around 25°C. Beach dinners in Bophut and Chaweng are comfortable after the day's shower has passed, and sunsets on the west coast can be spectacular when the clouds break.
Two weeks in August
For a longer August stay, combine Samui with a few nights on Koh Phangan or Koh Tao. Ferries run several times a day, and moving islands mid-trip breaks up a long holiday for children and adults alike.
Koh Tao and Koh Nang Yuan day trip
August's often calm Gulf makes this a good month for the long crossing. Check the forecast and the operator's weather policy.
Check on the listing before you book
- How long the crossing takes
- The weather and cancellation policy
- Island entry fees on the day
Powered by GetYourGuide. Price, duration and availability depend on your date.
Koh Samui Weather August: Day Trips
Samui is the hub for day trips in the Gulf of Thailand. In August, the average wind at the Ko Samui station is 2.7 knots from the west, which decides how comfortable the crossings are. Shorter trips are the safer choice whenever the forecast is borderline.
| Trip | In August |
|---|---|
| Ang Thong Marine Park | Open outside the annual closure; can close for a day in rough seas. |
| Koh Phangan | Short, usually smooth crossing. |
| Koh Tao and Koh Nang Yuan | Long crossing, usually workable; check the forecast. |
| Pig Island and the southern islands | Short trips, the easiest choice on a borderline day. |
Whatever the month, book day trips early in your stay so you can move them, and read each operator's weather and cancellation policy. Our guides to Ang Thong, getting to Koh Phangan and Koh Nang Yuan cover each trip in detail.
Koh Samui Weather August: Day Trips to Koh Phangan and Koh Tao
Koh Phangan is the closest neighbour, a short ferry ride from the north coast. Koh Tao is further and best done on a calm day; Koh Nang Yuan, three islands joined by sandbars off Koh Tao, is the classic snorkel stop.
Check the forecast the evening before and pick a morning departure. If you are prone to seasickness, take tablets before you board and sit near the back of the boat.
Our Samui to Koh Phangan guide and Koh Nang Yuan guide cover routes and timings.
Koh Samui Weather August: Who It Suits
August suits families and island-hoppers.
- Families. Calm east-coast beaches and plenty of indoor backups.
- Island-hoppers. Often good conditions for Koh Phangan and Koh Tao.
- Couples. Warm evenings and sunset dinners.
- Budget travellers. Low season, but family rooms in demand.
- Snorkellers. Calm mornings around Koh Tao and Ang Thong.
Koh Samui Weather August: A 5-Day Plan
A plan with two island days and a spare day.
- Day 1. Arrive, swim at Chaweng or Choeng Mon.
- Day 2. Koh Tao and Koh Nang Yuan day trip.
- Day 3. Spare or rest day: spa, pool, Fisherman's Village.
- Day 4. Ang Thong or a Koh Phangan day trip.
- Day 5. Big Buddha early, Lamai in the afternoon, night market dinner.
Koh Samui Weather August: Prices and Crowds
August is low season on paper, but European summer holidays keep family rooms and villas in demand.
Compare live prices for your dates rather than relying on percentages quoted online.
Koh Samui Weather August: Packing and Getting Around
Pack for sun, heat and boat days.
- Seasickness tablets
- Reef-safe mineral sunscreen and rash guards
- A dry bag
- A compact umbrella
- Water shoes
Taxis and ride-hailing apps are easy to find. If you ride a scooter, slow down after showers. If you plan to ride, read our scooter rental guide first, and keep data on your phone with an eSIM for Thailand so you can check radar and messages on the road.
Koh Samui Weather August: Health and Safety
Heat is the main health risk in August, with average highs of 32.4°C and humidity around 78%. Drink water before you feel thirsty, add electrolytes on long days out, and keep the hours between 11 am and 3 pm for shade, the pool or a long lunch.
Mosquito-borne illnesses such as dengue occur in Thailand all year and are more common in the rainy season. Use repellent, especially at dawn and dusk, and choose rooms with screens or air conditioning.
Helmets are compulsory for scooter riders in Thailand, and road accidents are the most common cause of serious injury for visitors. Ride slowly, avoid riding after drinking, and make sure your travel insurance covers scooters if you plan to ride.
Travel insurance that covers medical care and weather-related changes is worth having whatever the month.
Koh Samui Weather August: Getting Here
Most visitors arrive either by air into Samui's own airport, mainly with flights from Bangkok, or by flying or taking the train or bus to Surat Thani and crossing by ferry from Donsak to Nathon or Lipa Noi. The ferry route is usually cheaper and takes longer.
August includes the European summer holidays, one of the busier travel periods, so book flights and ferry transfers early.
Crossings are usually smooth, with occasional delays after a squall.
Compare ferries and flights on 12Go for your dates, and see our Koh Samui ferry guide for the routes. Ferries to Koh Phangan and Koh Tao usually run normally; squalls can cause short delays.
Koh Samui Weather August: Booking Tips
- Book family rooms early.
- Schedule island trips early in your stay.
- Read the weather and cancellation policy of each tour.
- Leave a buffer day before international flights.
Booking a few weeks ahead and reading the conditions of each rate matters more than chasing the lowest headline price.
Koh Samui Weather August vs July and September
| Month | Rainfall | Rainy days | High / low | Wind |
|---|---|---|---|---|
| July | 117.0 mm | 14.3 | 32.3°C / 25.1°C | 2.5 kn, west |
| August | 102.2 mm | 14.5 | 32.4°C / 25.1°C | 2.7 kn, west |
| September | 117.5 mm | 15.0 | 31.9°C / 24.8°C | 2.6 kn, west |
August has the lowest rainfall of the summer months. September has similar rain over slightly more days, before the sharp rise in October. To weigh every month side by side, use our best time to visit Koh Samui guide.
The bottom line on Koh Samui weather August
August is the driest of Samui's summer months on averages, with short showers on about 14 days and often calm seas on the east coast. It is a good month for island day trips; book family rooms early.
Koh Samui Weather August: FAQ
Is August a good time to visit Koh Samui?
Yes for most travellers. It has the lowest rainfall of the May to September period, short showers and an often calm east coast.
How much does it rain in Koh Samui in August?
The 1991–2020 average is 102.2 mm over 14.5 rainy days at the Thai Meteorological Department's Ko Samui station.
Can you visit Koh Tao from Samui in August?
Usually, yes. Pick a calm day and check the operator's weather policy.
Which beaches are calm in August?
Usually the east and north-east coasts, because the wind blows mostly from the west.
Is August busy on Koh Samui?
Busier than May and June because of European summer holidays, especially for family rooms.
Is August hot on Koh Samui?
Yes. The average high is 32.4°C and the average low 25.1°C at the Ko Samui station.
Is August good for snorkelling?
Often, on calm mornings. Koh Tao, Koh Nang Yuan and Ang Thong are usually accessible.
Ready to book August?
Compare rooms for your exact dates. Questions about day trips? Ask a local on WhatsApp from the menu.
See what follows in our September guide, or compare with July.
Sources for Koh Samui Weather August
Climate figures on this page come from the Thai Meteorological Department's 30-year climate normals. Other facts were checked on 13 November 2026 against the sources below. Weather, park rules and event dates can change, so confirm locally before you travel.
- Thai Meteorological Department: climatological data for the period 1991–2020 (Ko Samui station 48550)
- Thai Meteorological Department: forecasts and warnings
- Tourism Authority of Thailand
How we put this guide together
Every climate figure on this page comes from one official dataset, the Thai Meteorological Department's 1991–2020 normals for the Ko Samui station, so the August numbers can be compared fairly with every other month in our series. We do not publish rain probabilities by week, sunshine hours or sea temperatures, because no official Samui series supports them.
Dates for parks, festivals and holidays were checked against the sources listed above. Prices change daily, so we point you to live availability instead of quoting rates. We update this guide when an official date or rule changes.
Disclosure: InsideSamui may earn a commission when you book through some links on this page, at no extra cost to you. Tour listings are provided by GetYourGuide. Prices, park rules and event dates change, so always confirm before you travel.