Pig Island in May: Weather, Sea Conditions and Tours

Is May a Good Time to Visit Pig Island?

Yes. May suits you if you want:

• a warm sea;
• fewer people than in the peak dry season;
• lower shoulder-season prices;
• normal tour availability.

You trade that for less predictable weather. You may get a bright, calm morning followed by a short afternoon shower, or a cloudy day with hardly any rain at all. A rain icon in your weather app is not a cancelled boat trip.

How Hot Is Koh Samui in May?

May is Koh Samui’s hottest month on average. The average daytime high is about 33°C and the air is humid, with average relative humidity close to 80 %.

On a boat the sun feels stronger than the thermometer suggests, because the water reflects it back at you. Bring:

• high-SPF sunscreen;
• a hat;
• a rash vest;
• plenty of water.

Is May Hotter Than April?

Slightly. The average high is about 33°C in May and 32°C in April, so both months feel very hot.

May is rainier and cloudier than April. That can take the edge off the sun on some days and make the air feel muggier on others. For Pig Island, an early departure is more comfortable than arriving at midday.

How Much Rain Does Koh Samui Get in May?

About 132 mm on average, spread over about 11 days with 1 mm of rain or more. For comparison:

May is noticeably wetter than February to April, close to June and September, and far drier than Koh Samui’s late-year rainy season. On your trip, that means roughly one day in three with some rain, usually not enough to stop a boat.

Does It Rain All Day in May?

Usually not. May rain often comes as:

• short tropical showers;
• evening rain;
• bursts of heavier rain;
• cloudy spells followed by sun.

Longer rainy stretches do happen. For boat-trip planning, the forecast for your day matters more than the monthly average.

Does the Chance of Rain Increase During May?

The number of rainy days nearly doubles between April (about 6) and May (about 11), as the island moves out of its driest stretch. Within May, one week is not reliably better than another, so you do not need to avoid the end of the month.

Do Pig Island Tours Run in May?

Yes. Koh Madsum and Koh Tan trips run through May, including:

• shared speedboats, such as the Pig Island and Koh Tan speedboat trip (4.5/5 from 5,629 reviews, from $42 per person);
• private longtails, such as the private longtail with snorkel gear (4.3/5 from 666 reviews, from $101 for up to two people);
• catamarans, such as the half-day catamaran trip to Koh Tan and Koh Madsum (4.2/5 from 165 reviews, from $67 per person);
• sunset tours, such as the Pig Island and Koh Tan sunset trip with dinner (4.2/5 from 734 reviews, from $46 per person);
• full-day island combinations, such as the full-day island-hopping trip to Pig Island and coral spots (4.6/5 from 3,655 reviews, from $51 per person).

There is no seasonal May closure. Trips stop only when the weather or sea makes them unsuitable.

Is Koh Madsum Closed in May?

No. Pig Island is open all year in practice. Individual operators set their own schedules, but there is no general May closure.

Is Koh Tan Snorkeling Good in May?

It can be. Koh Tan is the usual snorkeling stop on Pig Island tours, and in May conditions there depend on:

• wind;
• waves;
• recent rain;
• tide;
• water movement.

The sea is very warm, at about 30°C. Visibility is the bigger variable: after heavy rain or wind the water can be cloudy, while on a calm day snorkeling can be very good. Our Koh Tan island guide covers the reef itself.

Is the Sea Too Warm?

Not for most swimmers. May is one of the warmest months for the sea around Koh Samui, and the water can feel almost bath-like. You will not need a wetsuit for ordinary snorkeling.

Are Boat Conditions Rough in May?

Some days are. May is not a rough-sea month as a rule: many days are calm, others turn windy or choppy.

The Pig Island route has one advantage. Koh Madsum and Koh Tan sit just off southern Koh Samui, so you are not committing to a long open-water crossing. The captain still makes the final safety call.

Morning or Afternoon in May?

Morning is the better default.

Morning advantages

• slightly cooler;
• lower sun;
• easier for families;
• often less chance of the showers that build later in the day;
• the afternoon stays free.

Afternoon advantages

• a relaxed start;
• softer light;
• the chance of a sunset.

If the forecast looks unsettled, choose a morning trip.

Is May Good for Sunset Tours?

Yes, if the forecast is stable. Some cloud can make a sunset more dramatic, but heavy cloud can hide the sun completely. A sunset tour puts you on the water at the right time, but the sunset itself is never guaranteed.

Is May Crowded?

Usually less than the peak dry-season months. You may find:

• private boats easier to book;
• fewer large tour groups;
• quieter beaches.

Weekends and Thai public holidays can still be busy.

Are Tours Cheaper in May?

Sometimes. May sits in a softer demand period, so you may find:

• lower hotel rates;
• better availability;
• the occasional tour promotion.

Do not expect every Pig Island tour to be discounted. Private boats are mostly priced by boat and route, and our Pig Island tour prices guide lists what each type costs.

Should You Book in Advance?

Yes, especially if you want:

• a private longtail;
• a morning slot;
• a small-group tour;
• a catamaran.

Choose free cancellation, because May weather can change at short notice.

How Many Backup Days Should You Leave?

One is usually enough. On a five-day stay, book Pig Island for day two or three. That leaves room to move it if:

• the weather turns;
• the sea is rough;
• the operator reschedules.

Do not put your only boat trip on your final morning.

What Happens If It Rains?

Light rain may change nothing, and the trip may still run. Worse conditions can mean:

• a delayed departure;
• a different snorkeling stop;
• a new date;
• a cancellation.

The captain watches wind, waves and thunderstorms more closely than the chance of rain in a forecast. Our guide to what to expect on a Pig Island tour covers the day itself.

What Should You Wear in May?

Wear:

• swimwear;
• light, breathable clothes;
• sandals or water shoes;
• a hat;
• sunglasses.

A rash vest is very useful in the strong sun.

What Should You Bring?

Bring:

• a towel;
• sunscreen;
• water;
• a dry bag;
• a waterproof phone case;
• a change of clothes;
• cash;
• a light rain layer.

The rain layer can be thin. You are in hot tropical weather.

Is a Longtail Good in May?

Yes, on calm days. A private longtail works well for Koh Tan and Pig Island, but it is more exposed than a larger boat, and the ride can feel bouncy in a chop.

Is a Speedboat Better?

Not necessarily. Speedboats are faster, but they bounce in a chop too. Choose one to save time, not for comfort.

Is a Catamaran Better?

For comfort, often yes. A catamaran usually has:

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

That helps in hot weather. Our catamaran vs speedboat vs longtail guide compares all three boats.

Is May Good for Families?

Yes. Heat is the main challenge, so families should:

• choose a morning trip;
• use strong sun protection;
• bring extra water;
• keep the rest of the day light.

A half-day Pig Island trip suits families best, and our half-day vs full-day guide explains why.

Is May Good for Couples?

Yes. In May:

• private boats can be easier to book;
• crowds can be smaller;
• afternoon and sunset trips work well on stable days.

Is May Good for Beginner Snorkelers?

Yes, on calm days. Koh Tan is a common spot for beginners. Wear a life jacket if you need one.

May vs April

April is drier, with about 83 mm of rain over 6 days against about 132 mm over 11 in May. Both are hot. If you can choose on weather alone, April is slightly easier.

May vs June

They are very similar. June gets about the same rain (about 134 mm over 10 days) and is a fraction cooler, with an average high just under 33°C. Neither is a bad month for Pig Island.

May vs September

May is about a degree hotter. September is slightly drier (about 118 mm against 132 mm), with the same number of rainy days, but it leads into October and November, Koh Samui’s wettest months. For a boat trip, the two months are about as reliable as each other; see our Pig Island in September guide for that month.

May vs November

May is much easier. November is Koh Samui’s wettest month, with about 445 mm of rain on average, and a much higher risk of rough seas.

Best May Booking Strategy

1. Book early in your stay.
2. Choose a morning departure.
3. Use free cancellation.
4. Keep one backup day.
5. Check the marine forecast close to departure.
6. Follow the captain’s safety decision.

Frequently Asked Questions

Is May a good month for Pig Island?

Yes. It is hot and wetter than April, but tours keep running and many days are suitable.

Does it rain every day in May?

No. Koh Samui averages about 11 days with 1 mm of rain or more in May.

How much rain does Koh Samui get in May?

About 132 mm on average (1991–2020 climate normals).

Is the sea warm?

Very. The sea is about 30°C in May.

Do Pig Island tours run in May?

Yes.

Is Koh Madsum closed in May?

No.

Is snorkeling good?

It can be excellent on calm days.

Is morning better?

Usually, because May is hot and showers can build in the afternoon.

Is May crowded?

Usually less than the peak dry-season months.

Can tours be cancelled?

Yes, if wind, storms or waves make conditions unsafe.

Planning a May Trip

May is a good month for Pig Island if you are comfortable with tropical heat and some uncertainty about the weather. It is wetter than February to April, and still far from Koh Samui’s late-year rainy season.

Expect:

• hot temperatures;
• a very warm sea;
• humid air;
• occasional showers;
• plenty of days when boats run normally.

Choose a morning tour, book early in your stay and keep one backup day. In May you get warm water, smaller crowds and an easy trip to Koh Madsum and Koh Tan.

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