Pig Island in September: Weather, Rain and Boat Conditions

Is September a Good Month for Pig Island?

Yes, if you go in with realistic expectations. September is less dependable than the dry months from late January to April, but it is much better than the words “rainy season” suggest.

You can still get:

• bright mornings;
• calm water;
• good snorkeling;
• a warm sea;
• normal Pig Island tours.

You can also get:

• showers;
• grey skies;
• stronger wind;
• changes at short notice.

A September trip works if you stay flexible.

Does It Rain All Day in September?

Usually not. Samui’s weather changes quickly, and a typical changeable day might bring:

• sun in the morning;
• cloud building later;
• a tropical shower;
• dry weather again afterward.

Longer spells of rain do happen. On average, though, about 11 September days get 1 mm of rain or more, so most days stay dry.

How Much Rain Does Koh Samui Get in September?

About 118 mm on the 1991–2020 average, a little more than August.

That is far below the late-year peak. The long-term averages for the station are:

• August: about 102 mm
• September: about 118 mm
• October: about 295 mm
• November: about 445 mm, the wettest month

So on your trip, September rain is likely to cost you a few hours, while a November week can cost you whole boat days.

Is September the Monsoon Season?

Think of September as the run-up to Koh Samui’s rainy period. Samui does not follow the same monsoon calendar as Phuket or Krabi: the island misses most of the southwest monsoon that soaks the Andaman coast from May, and its heavy rain arrives with the northeast monsoon from October. September sits between the two, which is why boat trips still run while the weather becomes more changeable.

Do Pig Island Tours Run in September?

Yes. Pig Island trips are not limited to the dry season, and September comes before the October to December wet months. Trips may use:

• a longtail;
• a speedboat;
• a catamaran.

They usually include Koh Tan snorkeling and the Pig Island beach, and some add kayaking or lunch.

Weather can still cancel a departure on a given day. Pick your exact date in the calendar above to see which trips are listed.

Is Pig Island Closed in September?

No. We know of no seasonal closure on Koh Madsum. When a tour does not run on a particular date, the reason is usually:

• the operator’s schedule;
• the weather;
• boat availability;
• demand.

That is not the island closing for the season.

What Are Sea Conditions Like?

The sea changes far more from day to day than the air temperature. On a calm September morning the short crossing from Thong Krut or Bang Kao is easy.

After wind or storms, the sea can be:

• choppy;
• uncomfortable on a small boat;
• murkier for snorkeling.

That is why Pig Island tours run on sea conditions, not on whether your weather app shows a rain cloud.

Is the Sea Warm Enough for Swimming?

Yes. The Gulf of Thailand stays warm in September, and cold water is not a concern. You can comfortably:

• swim;
• snorkel;
• paddle;
• spend a long time in the water.

Water clarity and waves matter much more than temperature.

Is Snorkeling Good in September?

It can be. Koh Tan is the main snorkeling stop on Pig Island tours, and good September snorkeling depends on:

• wind;
• waves;
• recent rain;
• the tide;
• local visibility.

A calm morning after settled weather can be very good. A windy day after heavy rain can leave the water cloudy. If snorkeling is your main reason for going, ask the operator about recent conditions, and see our Koh Tan island guide for the reef itself.

Morning or Afternoon in September?

Morning is the safer default.

Why morning can be better

• cooler temperatures;
• more of the day left afterward;
• a lower risk of the showers that build later in the day;
• often calmer conditions.

Not every morning is perfect and not every afternoon is bad. If you only have one realistic tour day, though, a morning boat gives you the better odds.

Can Afternoon Tours Still Be Good?

Yes. An afternoon trip can work well if:

• the forecast is stable;
• you want softer light;
• you dislike early starts;
• you want to avoid the morning boats.

Private charters give you the most freedom to pick the hour.

Is September Crowded?

Usually quieter than July and August, when the European school holidays fall, and quieter than the December–April high season. That can mean:

• easier tour availability;
• fewer large groups;
• more choice of private boats.

Crowds still vary from day to day.

Is September Cheaper?

Sometimes. Hotels and tours can be priced more keenly outside the high season. Do not expect every Pig Island tour to be discounted, though: private boat prices depend more on:

• the boat;
• the route;
• the duration;

than on the season.

Should You Book in Advance?

Yes, but choose flexible terms. In September the cancellation policy matters more than in February.

Look for:

• free cancellation (every Pig Island tour we list on GetYourGuide offers it; check the cut-off time on your listing);
• rescheduling if the weather turns;
• a refund if the operator cancels;
• an easy date change.

That gives you room to react to the conditions.

How Many Backup Days Should You Leave?

At least one, and two is better. On a five-day stay, avoid putting Pig Island on your last day.

A better plan:

• book it for day 2;
• keep days 3 and 4 free as backup.

That takes most of the stress out of the weather.

What Happens If the Weather Is Bad?

Possible outcomes:

• the tour runs normally;
• the snorkeling spot changes;
• departure is delayed;
• the tour is moved to another day;
• the tour is cancelled.

The captain makes the final safety call. Do not push an operator to leave just because the rain has stopped: the wind and waves may still be poor. Our guide to what to expect on a Pig Island tour covers the day itself.

Should You Trust a Weather App?

Use it as a guide, not a verdict. A phone app may show a rain icon for a day that stays mostly dry.

For a boat trip, these matter more:

• wind;
• wave height;
• thunderstorms;
• recent local conditions.

If your operator says the trip is running normally, that tells you more than a generic daily icon.

Longtail or Speedboat in September?

Both work.

Longtail

Best for:

• private groups;
• atmosphere;
• the short route.

It is more exposed when the sea is choppy. The shared longtail trip with a viewpoint hike (4.3/5 from 917 reviews, from $28 per person) is the lowest-priced option with transfers and the island fee included.

Speedboat

Best for:

• faster transfers;
• organised tours.

It can still bounce in rough water. The Pig Island and Koh Tan speedboat trip (4.5/5 from 5,627 reviews, from $42 per person) is the most-reviewed Pig Island tour we list.

Neither boat turns a bad sea into a good one.

Is a Catamaran Better in September?

It can be. A catamaran usually offers:

• more deck space;
• a steadier platform;
• more shade;
• better facilities.

If comfort matters and the weather looks mixed, compare the Koh Madsum and Koh Tan speed catamaran (4.5/5 from 107 reviews, from $64 per person). Our catamaran vs speedboat vs longtail guide compares all three boats.

What Should You Bring in September?

Bring the usual Pig Island kit plus a little extra for the weather:

• swimwear;
• a towel;
• sunscreen;
• a rash vest;
• a hat;
• sunglasses;
• a dry bag;
• a waterproof phone pouch;
• a light rain layer;
• a change of clothes;
• cash for the 50-baht island fee if your tour does not include it.

A dry bag is especially useful in September.

Will Rain Ruin Pig Island?

Not necessarily. Light cloud can make the beach more comfortable, and the pigs will still be there. You can still:

• take photos;
• swim;
• relax;
• snorkel if conditions allow.

A rough sea affects the day far more than a short shower does.

Are the Pigs Still There in September?

Yes. The pigs live on Koh Madsum all year. The weather affects the boat trip, not whether the pigs are there.

Is September Good for Families?

Yes, if you keep the plan flexible. Families should:

• choose a morning departure if possible;
• check that child life jackets are on board;
• book a cancellable tour;
• avoid putting the trip on the last day.

A private longtail works well because you control the pace.

Is September Good for Couples?

Yes. Couples often like:

• the smaller crowds;
• private longtail options;
• afternoon departures on settled days.

If you care about photos, cloud gives softer light than the hard midday sun of the dry season.

Is September Good for Snorkeling Beginners?

Yes, on calm days. Koh Tan suits beginners on many tours. Wear a life jacket if you need one and follow the guide. If the water is too rough, the operator may change the snorkeling plan. Our Koh Samui snorkeling comparison covers the other reefs.

September vs August

September is a little wetter and more changeable: about 118 mm of rain against 102 mm in August. The difference is small, and it is no reason to avoid September.

September vs October

September is generally the better month. Average rainfall more than doubles in October, to about 295 mm, and rainy days rise from about 11 to about 16. If you can choose between late September and late October for a reliable boat day, pick September.

September vs November

September is much better. November is Koh Samui’s wettest month, at about 445 mm on average, and it is when Pig Island trips are most often cancelled.

September vs February

February is more reliable. It is the island’s driest month, at about 64 mm, so if the weather is all you care about, February wins.

September still offers:

• a warm sea;
• smaller crowds;
• plenty of tours running.

Best September Booking Strategy

1. Book Pig Island early in your stay.
2. Choose free cancellation.
3. Prefer a morning boat if the weather is unsettled.
4. Keep one or two backup days.
5. Confirm conditions with the operator the evening before.
6. Let the captain make the final safety call.

That is enough for most travellers.

Frequently Asked Questions

Is September a good time for Pig Island Koh Samui?

Yes. Tours run, the sea is warm and September comes well before the November rain peak.

Does it rain every day?

No. Showers are common but often short, and on average about 11 September days get 1 mm of rain or more.

How much rain does Koh Samui get in September?

About 118 mm for the month on the 1991–2020 average.

Is September the wettest month?

No. November is, at about 445 mm.

Do Pig Island tours operate in September?

Yes, subject to the sea conditions on the day.

Is Koh Madsum closed in September?

We know of no seasonal closure; check your date in the booking calendar.

Is snorkeling possible?

Yes, especially on calmer days at Koh Tan.

Is the sea cold?

No. The Gulf of Thailand stays warm in September.

Is morning better?

Usually, as the safer default when the weather is unsettled.

Can tours be cancelled?

Yes, if wind or waves make the crossing unsafe.

Should I book my last holiday day?

No. Leave at least one backup day.

Planning a September Trip

September is a reasonable month for Pig Island if you stay flexible. It is not as dry or predictable as February to April, and it is not Koh Samui’s peak rainy period either.

Expect:

• warm temperatures;
• a warm sea;
• some showers;
• more cloud;
• choppy water on some days;
• Pig Island tours running on days with a suitable sea.

Book early in your stay, choose free cancellation and keep one or two backup days. On a calm September day, a Pig Island and Koh Tan trip is as good as one in the dry season.

Compare our current Pig Island tours from Koh Samui to see morning, afternoon, longtail, speedboat and catamaran trips, and check your September dates in the calendar, because schedules can change.