Dec → Feb
28°
nights 25°
- 16 rainy days · 135 mm
- sea 29°
When is the best time to visit Koh Samui?
- Jan28°recommended
- Feb28°recommended
- Mar30°recommended
- Apr31°recommended
- May31°fair
- Jun31°fair
- Jul31°recommended
- Aug31°recommended
- Sep30°fair
- Oct29°not recommended
- Nov28°not recommended
- Dec28°fair
RecommendedFairNot recommended· afternoon temperature
The weather in Koh Samui, month by month
The table of records, month by month
| Month | High | Low | Rainfall | Rainy days | Sea | Best |
|---|---|---|---|---|---|---|
| January | 28° | 25° | 132 mm | 17 d | 29° | ✓ |
| February | 28° | 25° | 47 mm | 12 d | 29° | ✓ |
| March | 30° | 26° | 38 mm | 10 d | 29° | ✓ |
| April | 31° | 27° | 106 mm | 14 d | 31° | ✓ |
| May | 31° | 27° | 107 mm | 19 d | 32° | |
| June | 31° | 27° | 77 mm | 16 d | 31° | |
| July | 31° | 26° | 99 mm | 18 d | 31° | ✓ |
| August | 31° | 26° | 80 mm | 18 d | 31° | ✓ |
| September | 30° | 26° | 145 mm | 20 d | 30° | |
| October | 29° | 25° | 220 mm | 27 d | 31° | |
| November | 28° | 25° | 286 mm | 26 d | 30° | |
| December | 28° | 25° | 226 mm | 20 d | 29° |
The four seasons in Koh Samui, in figures
What the 2015-2024 records (Chaweng) show, season by season, to compare at a glance instead of reading twelve rows of a table.
Mar → May
30 to 31°
nights 26 to 27°
- 14 rainy days · 84 mm
- sea 31°
Jun → Aug
31°
nights 26 to 27°
- 17 rainy days · 85 mm
- sea 31°
Sep → Nov
28 to 30°
nights 25 to 26°
- 24 rainy days · 217 mm
- sea 30°
Book early for January to April and July to August
The timing is right, so it is right for everyone: in these months the best places to stay and the small-group tours go first. Here is where to start.
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What to do in Koh Samui, month by month
EventsSongkranAprilLoy KrathongNovemberDetails ↓
favourablewith compromisesunfavourable
Beach & swimming: good conditions all twelve months.
Diving & snorkelling: good conditions all twelve months.
- Towns & culture: February, March
Grid derived from the records (temperature, rainfall, sea), not from an opinion.
What's on in Koh Samui, month by month?
What comes back every year, and when. One of these events fills the hotels and pushes prices up: something to aim for or to avoid, depending on what you want.
- AprilSongkran big crowds
In mid-April, Thai New Year turns into a water fight on Chaweng and Lamai, and many shops close for a few days.
- NovemberLoy Krathong
At the November full moon, small rafts of leaves and candles are set afloat on the sea and on the island's ponds.
Travelling off-peak
Month by month, in detail
January
Recommended28°25° at night
- 132 mm · 17 d
- sea 29°
High season, book early
February
Recommended28°25° at night
- 47 mm · 12 d
- sea 29°
High season, book early
March
Recommended30°26° at night
- 38 mm · 10 d
- sea 29°
Busy, without the crush
April
Recommended31°27° at night
- 106 mm · 14 d
- sea 31°
High season, book early
May
Fair31°27° at night
- 107 mm · 19 d
- sea 32°
Low season, lower prices
June
Fair31°27° at night
- 77 mm · 16 d
- sea 31°
Low season, lower prices
July
Recommended31°26° at night
- 99 mm · 18 d
- sea 31°
High season, book early
August
Recommended31°26° at night
- 80 mm · 18 d
- sea 31°
High season, book early
September
Fair30°26° at night
- 145 mm · 20 d
- sea 30°
Low season, lower prices
October
Not recommended29°25° at night
- 220 mm · 27 d
- sea 31°
Low season, lower prices
November
Not recommended28°25° at night
- 286 mm · 26 d
- sea 30°
Low season, lower prices
December
Fair28°25° at night
- 226 mm · 20 d
- sea 29°
Quiet, then the holidays
Read the twelve months in detail
January. 28 °C in the afternoon and 25 °C at night. Frequent rain: 132 mm over 17 days. The sea is at 29 °C, a proper swim. High season: book early.
February. 28 °C in the afternoon and 25 °C at night. Expect 12 days of rain in the month (47 mm). The sea is at 29 °C, a proper swim. High season: book early.
March. 30 °C in the afternoon and 26 °C at night. Expect 10 days of rain in the month (38 mm). The sea is at 29 °C, a proper swim. Busy season, without the crush.
April. 31 °C in the afternoon and 27 °C at night. Frequent rain: 106 mm over 14 days. The sea is at 31 °C, a proper swim. High season: book early.
May. 31 °C in the afternoon and 27 °C at night. Frequent rain: 107 mm over 19 days. The sea is at 32 °C, a proper swim. Low season: fewer people, lower prices.
June. 31 °C in the afternoon and 27 °C at night. Frequent but light showers: 77 mm over 16 days. The sea is at 31 °C, a proper swim. Low season: fewer people, lower prices.
July. 31 °C in the afternoon and 26 °C at night. Frequent rain: 99 mm over 18 days. The sea is at 31 °C, a proper swim. High season: book early.
August. 31 °C in the afternoon and 26 °C at night. Frequent but light showers: 80 mm over 18 days. The sea is at 31 °C, a proper swim. High season: book early.
September. 30 °C in the afternoon and 26 °C at night. Frequent rain: 145 mm over 20 days. The sea is at 30 °C, a proper swim. Low season: fewer people, lower prices.
October. 29 °C in the afternoon and 25 °C at night. A very wet month, 220 mm of rain over 27 days. The sea is at 31 °C, a proper swim. Low season: fewer people, lower prices.
November. 28 °C in the afternoon and 25 °C at night. A very wet month, 286 mm of rain over 26 days. The sea is at 30 °C, a proper swim. Low season: fewer people, lower prices.
December. 28 °C in the afternoon and 25 °C at night. Frequent rain: 226 mm over 20 days. The sea is at 29 °C, a proper swim. Quiet at the start of the month, then busier as the holidays approach.
Same season, other ideas
Their best time overlaps with this one: worth comparing before you book.
Frequently asked questions
When is the best time to visit Koh Samui?
January to April and July to August: over these months, recorded highs range from 28 to 31 °C, with 15 days of rain a month on average (2015-2024 records, Chaweng).
Which month should you avoid in Koh Samui?
November: it is the wettest of the months to avoid, with 286 mm over 26 days of rain on average, according to 2015-2024 records at the reference point (Chaweng).
What is the hottest month in Koh Samui?
April, with 31 °C on average in the afternoon and 27 °C at night. 2015-2024 records (Chaweng).
What is the coldest month in Koh Samui?
January, with 28 °C at best during the day and 25 °C at night. 2015-2024 records (Chaweng).
What is the driest month in Koh Samui?
March: 38 mm over 10 days of rain, against 286 mm in November, the wettest month.
When can you swim in Koh Samui?
The water never drops below 22 °C: from 29 to 32 °C depending on the month (warmest in May), measured in 2023-2024 on the nearest coast (Chaweng).
Plan this trip
📒 The free printable Koh Samui guide: itinerary, map, where to sleep→
🧭 When to visit Thailand: the country overview→
🗓️ Best time to visit: all our destinations→
Compare with other destinations
Photos: Lakshan Abey / Pexels · Lloyd Douglas / Pexels · Kamilokardona / CC BY-SA 3.0 (Wikimedia Commons) · Anna Zviahina 🇺🇦 / Pexels · Anetta Kolesnikova / Pexels · foad niestat / Pexels