Best time to visit Koh Samui
In short
The best time to visit Koh Samui is February to April, the driest months, ideally timed with a Full Moon.
February to April, and good through August
The best time to visit Koh Samui is February to April, when the island is driest and the sea is calm, with good weather through August.
Koh Samui, Koh Phangan and Koh Tao are driest from February to April and good through August, and wettest from October to December, with the most rain in November.
That's the opposite of Phuket, so Samui is the summer beach choice.
For a party trip, pick your month, then line it up with a Full Moon date.
- February–April
- February
- November (~445 mm)
- better than Phuket May–August
- closed 1 Nov–15 Dec 2026
Month by month
It runs from the dry, calm peak of February to the wettest month, November.
The Koh Samui weather by month in the table uses the island's long-term averages; the Met Office's Thailand weather guide explains the seasons.
Pick the month for the weather first, then see what's on that week.
Best time to visit Koh Samui month by month
January
- Weather:
- Dry, coolest, highs about 29°C
- Sea:
- Calm
- What's on:
- Peak season
February
- Weather:
- Driest month
- Sea:
- Calm
- What's on:
- Peak season
March
- Weather:
- Dry, hotter
- Sea:
- Calm
- What's on:
- Peak season
April
- Weather:
- Hot, about 32°C
- Sea:
- Calm, warmest sea
- What's on:
- Songkran, 13 to 15 April
May
- Weather:
- Hottest, about 33°C
- Sea:
- Calm
- What's on:
- Quieter
June
- Weather:
- Short daily showers
- Sea:
- Mostly calm
- What's on:
- Good beach weather
July
- Weather:
- Short daily showers
- Sea:
- Mostly calm
- What's on:
- Peak summer holidays
August
- Weather:
- Short daily showers
- Sea:
- Mostly calm
- What's on:
- Peak summer holidays
September
- Weather:
- Showers increase
- Sea:
- Mostly calm
- What's on:
- Quieter
October
- Weather:
- Rainy season starts
- Sea:
- Rougher
- What's on:
- Quieter
November
- Weather:
- Wettest month
- Sea:
- Roughest; Ang Thong closed
- What's on:
- Full Moon, 24 November
December
- Weather:
- Clearing through the month
- Sea:
- Calming
- What's on:
- Full Moon 24 December; New Year's Eve
When should you not go to Koh Samui?
If there's one month when not to go to Koh Samui, it's November, the wettest of the year. Expect rain in late October and early December too.
November brings about 445 mm of rain over 16 rainy days.
Ang Thong Marine Park is closed from 1 November to 15 December 2026, so the island's best boat day is off; Tanner swaps in a villa pool day.
If your dates fall in November, Phuket is the better beach.
AIWhen is the rainy season on Samui?
It runs from October to December, when the northeast monsoon reaches the Gulf, wettest in November.
December clears through the month, ready for the New Year's Eve parties.
The clubs, villas and Chaweng's bars run all year. Read our Thailand rainy season guide before you commit to a wet month.
AIKoh Samui in summer: June to September
June to August is the summer pick: the Gulf stays mostly dry while the Andaman coast is in its monsoon.
From June to September, the Gulf islands get 100 to 135 mm of rain a month on 10 to 11 rainy days: beach weather with a daily shower.
July and August are the busiest summer months, with school holidays in Europe.
For a summer group trip, Samui beats Phuket. See Koh Samui vs Phuket, and ask Tanner to hold a villa for July.
When is the best Full Moon to go?
For a party trip, go the week of a Full Moon, with the party on Koh Phangan's Haad Rin beach, one island away.
The next Full Moon dates are 24 November and 24 December 2026, with a countdown party on 31 December.
Between Full Moons, the Halfmoon Festival sells its one-day Magic Forest pass at ฿2,700, with a speedboat package at ฿1,600.
The driest Full Moons fall from February to April. See the Full Moon Party guide, and ask Tanner to book the boat across.
Samui or Phuket, by month
Samui wins from May to August, when it's dry and Phuket is in its monsoon; both are good from February to April, and Phuket wins from October to December.
In November and December, Samui gets its heaviest rain and Phuket is the better beach.
Samui is quieter, with villas and the Full Moon Party one island away; Phuket is bigger, with Patong and the superclubs.
Our Koh Samui vs Phuket guide has the rest; read it before you pick.
How many days do you need on Samui?
Three or four days are enough in Koh Samui: one boat day to Ang Thong (closed 1 November to 15 December 2026, so a villa pool day then), one island day and one beach day, plus a Full Moon if the dates fit.
Add a day for Koh Phangan or Koh Tao.
In the dry season, book the boat early: Ang Thong is the island's best day.
Fill the days from our things to do in Koh Samui list.
October and December: the edge months
October is the start of the wet season, so the first half of the month is the better bet. The villas are quiet and easy to book.
December clears as it goes. The second half is the one to aim for, with the 24 December Full Moon and New Year's Eve on the calendar.
Ang Thong reopens around 15 December, so a late-December trip gets the boat day back.
Tanner's pick for a winter trip: 20 to 31 December, the Full Moon and the countdown in one week.
Crowds and booking by season
January to April and July to August are the busy stretches, and Christmas to New Year is the busiest week of all.
The big pool villas go first in those weeks, then the boats for Full Moon nights.
May, June and September are the quiet sweet spots: good weather, fewer people and an easy choice of villas.
For a peak-week trip, lock the villa before the flights.
Koh Samui's seasons in short
- February to April is the driest time on Koh Samui, and February is the driest month.
- June to September brings short daily showers, with 100 to 135 mm of rain a month.
- The rainy season runs from October to December, and November is the wettest month at about 445 mm.
- May is the hottest month, with highs of about 33°C.
- Ang Thong Marine Park closes from about 1 November to 15 December.
- Samui is the better island from May to August, when Phuket is in its monsoon.
Checked October 2026.
Next: pick your month
The next step is to pick your month: February to April for the driest weather, June to August for summer, and a Full Moon week for the party.
Then add the villa, the boat and the club, with the van waiting between them.
Plan it with Tanner, and he sends back the plan for your dates.
AI
Written by Tanner Altman · Updated 7 November 2026
Questions
Questions groups ask about Koh Samui's seasons
What is the best month to visit Koh Samui?
February, the driest month, or any month from February to April. The island stays good through August, with short daily showers from June to September.
When is the rainy season in Koh Samui?
October to December, with November the wettest month, at about 445 mm of rain over 16 rainy days. Late October and early December are wet too.
Is Koh Samui good in July and August?
Yes. The Gulf stays mostly dry in summer, with short daily showers, while Phuket and the Andaman coast are in their monsoon. It's one of the best summer beach choices in Thailand.
Is Koh Samui good in November?
No, not for a beach trip. November is Samui's wettest month, and Ang Thong Marine Park is closed from 1 November to 15 December 2026. Phuket is the better beach in November.
What is the hottest month in Koh Samui?
May is the hottest month, with average highs of about 33°C, followed by April at about 32°C. December and January are the coolest months on the island.
When is the next Full Moon Party?
The next Full Moon Parties are on 24 November and 24 December 2026, at Haad Rin on Koh Phangan, with a countdown party on 31 December. Base on Samui and take the boat over.
What is the rainy season in Koh Samui like?
Heavy showers and rougher seas from October to December, worst in November. The bars, clubs and villas stay open, but boat days depend on a calm morning.
Is October a good time to visit Koh Samui?
Early October can still be good, but it's the start of the wet season. You'll find quiet beaches and easy villa bookings, with more rain as the month goes on.
Is Koh Samui or Krabi better?
It depends on the month. Krabi is on the Andaman coast, best from November to April, while Samui stays good through August. For a summer trip, Samui wins.
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Credits: top photo by Photo: YuvalH / Flickr, CC BY 2.0.