Koh SamuiPhoto: Sonia Selivonchik · CC BY-SA 4.0Thailand · Asia
Best time to visit Koh Samui
Koh Samui lies in the Gulf of Thailand and has a different rainy season from the Andaman coast: it is driest from about January to April/May, while October to December is the wettest. Warm year-round with a warm sea.
Climate decision
Best travel months for Koh Samui
Top recommendation
Next highest scores
Historical monthly averages, not a weather forecast. Individual days and years can differ substantially.
Latest 5-year values 2021–2025
Average of the five most recent complete years compared with the 1991–2025 climate average.
February · Monthly precipitation
122.4 mm/month
1991–2025: 59.3 mm/month
+63.2 mm/month · higher
February · Wet days
10 days/month
1991–2025: 6.6 days/month
+3.4 days/month · higher
November · Sunshine per day
4.6 h/day
1991–2025: 5.2 h/day
-0.6 h/day · lower
June · Mean daily maximum
30 °C
1991–2025: 29.5 °C
+0.5 °C · higher
May · Sea temperature
30.7 °C
1991–2025: 30.4 °C
+0.3 °C · similar
May: 94/155 days at or above 30 °C; highest single value 33.5 °C.
Five-year historical sample, not a weather forecast or long-term climate trend. Individual hot days can be far above the monthly mean.
Annual profile · Rainfall rhythm
Koh Samui: rainfall separates the travel months
The driest and wettest months are 21.7 rainy days apart. Average daily highs vary by 2.6 °C, so both signals matter when choosing a month.
What matters
A warmer month is not automatically the most reliable. Read the drier windows alongside sunshine, sea temperature and the activity you have in mind.
Fewest rainy days
February · 6.6
Most rainy days
October · 28.2
Most sunshine
March · 7.5 h
Warmest sea
May · 30.4 °C
Month by month
Overall suitability per month. Tap a month for details.
All climate figures compared
The table is the complete accessible data view; the charts below highlight selected patterns.
| Month | Avg high °C | Avg low °C | Rainy days (est.) | Rain mm | Sun h/day (est.) | Humidity % | Wind m/s | Sea °C | Score |
|---|---|---|---|---|---|---|---|---|---|
| January | 27 | 26 | 13 | 111 | 6.0 | 79 | 4.1 | 28 | 73 |
| February | 28 | 26 | 7 | 59 | 7.0 | 79 | 3.7 | 28 | 83 |
| March | 29 | 27 | 9 | 94 | 7.5 | 78 | 3.3 | 29 | 75 |
| April | 30 | 28 | 14 | 93 | 7.5 | 77 | 2.9 | 30 | 62 |
| May | 30 | 28 | 26 | 173 | 6.8 | 78 | 3.3 | 30 | 50 |
| June | 30 | 28 | 25 | 164 | 6.4 | 80 | 4.0 | 30 | 52 |
| July | 29 | 28 | 27 | 172 | 6.3 | 80 | 4.3 | 30 | 54 |
| August | 29 | 27 | 27 | 163 | 6.5 | 81 | 4.4 | 29 | 55 |
| September | 29 | 27 | 27 | 181 | 6.3 | 81 | 4.0 | 29 | 56 |
| October | 28 | 27 | 28 | 265 | 5.6 | 82 | 3.4 | 29 | 56 |
| November | 28 | 27 | 25 | 396 | 5.2 | 81 | 4.3 | 29 | 57 |
| December | 28 | 26 | 18 | 253 | 5.3 | 80 | 4.7 | 28 | 64 |
Climate through the year
Compare temperature, rainy days, sunshine and, for coastal destinations, sea temperature month by month.
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Where to stay in Koh Samui
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The number is the overall climate score, not a similarity score.
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Frequently asked questions
When is the best time to visit Koh Samui?
The strongest climate months are January, February, March, December. Values are historical averages, not a forecast.
Which month has the highest average daily maximum temperature in Koh Samui?
Average daily maximum temperatures in Koh Samui are practically tied in April and May at around 30 °C.
When is the sea warmest at Koh Samui?
In May, at around 30 °C.