Climate in Koh Samui — Annual Weather Overview
Koh Samui has a tropical climate — hot and humid year-round with a distinct wet season. The hottest month is April (average high 31.1°C) and the coolest is December (27.9°C). Temperatures are consistent year-round, with highs ranging only 3.2°C between the warmest and coolest months. Annual rainfall totals around 1672mm. November is the wettest month at 323.1mm, while March averages just 36.5mm. Average daily sunshine is 9.7 hours.
**Spring (March, April, May):** average highs 30.9°C, 278mm rain. **Summer (June, July, August):** average highs 30.3°C, 366mm rain. **Autumn (September, October, November):** average highs 28.6°C, 764mm rain. **Winter (December, January, February):** average highs 28.5°C, 263mm rain.
Koh Samui — Monthly Temperatures
Koh Samui — Monthly Rainfall
✅ Best months to visit
All year
ℹ️ No months to avoid
Weather in Koh Samui stays reasonable all year.
Koh Samui weather by month
| Month | High | Low | Rain | Sun/day | Rainy days | Rating |
|---|---|---|---|---|---|---|
| January | 28.5°C | 24.3°C | 43.1mm | 10.4h | 14 | 10/10 |
| February | 29.0°C | 24.5°C | 58.2mm | 10.5h | 14 | 10/10 |
| March | 30.5°C | 25.4°C | 36.5mm | 10.9h | 9 | 10/10 |
| April | 31.1°C | 26.3°C | 106.9mm | 10.7h | 16 | 9/10 |
| May | 31.0°C | 26.5°C | 134.5mm | 10.4h | 20 | 9/10 |
| June | 30.6°C | 26.2°C | 102.4mm | 10.3h | 18 | 9/10 |
| July | 30.0°C | 25.9°C | 149.9mm | 8.8h | 22 | 9/10 |
| August | 30.4°C | 26.0°C | 114.2mm | 9.4h | 21 | 9/10 |
| September | 29.2°C | 25.4°C | 196.8mm | 8.5h | 22 | 9/10 |
| October | 28.5°C | 24.8°C | 244.4mm | 8.5h | 28 | 8/10 |
| November | 28.1°C | 24.5°C | 323.1mm | 8.0h | 26 | 8/10 |
| December | 27.9°C | 24.4°C | 161.7mm | 9.7h | 19 | 9/10 |
For the full verdict on when to go, see the best time to visit Koh Samui and the Koh Samui rainy season guide. Seasonal breakdowns: spring, summer, autumn and winter.
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Frequently Asked Questions
What type of climate does Koh Samui have?
Koh Samui has a tropical climate — hot and humid year-round with a distinct wet season. Average highs range from 27.9°C in December to 31.1°C in April.
What is the hottest month in Koh Samui?
April is the hottest month in Koh Samui, with average highs of 31.1°C and lows of 26.3°C.
What is the coldest month in Koh Samui?
December is the coolest month, with average highs of 27.9°C and lows of 24.3°C.
What is the wettest month in Koh Samui?
November is the wettest month, averaging 323.1mm of rainfall over around 26 rainy days.
When is rainy season in Koh Samui?
Rainy season in Koh Samui runs April to December, when rainfall is significantly higher than the rest of the year. Full rainy season guide →
How much rain does Koh Samui get per year?
Koh Samui receives around 1672mm of rain per year. The driest month is March (36.5mm).
When is the best time to visit Koh Samui?
The best time to visit Koh Samui is All year. See the full month-by-month guide →
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For the packing side of things, our sister site has a ready-made checklist: Koh Samui packing list at 247PackingList. For currency, language and country facts see the Thailand guide at 247CountryInfo. Some travellers fund a longer stay in Koh Samui by teaching English along the way — a TEFL certificate is usually all it takes.
Trip essentials for Koh Samui
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Climate data sourced from Open-Meteo (open source, open data licence). Monthly averages calculated from 2020–2023 historical data. Weather can be unpredictable — always check a live forecast before travelling.