Koh Samui · AutumnMonth summary
Koh Samui weather in September
✅ Good
🌡️ Temperature min / max
26°C – 30°C
🌧 Rainy days
67% of days
☀️ Sunshine
10.0h per day on average
🌊 🌊 Season
Autumn
⭐ ⭐ Weather score
7.1/10
📅 📅 Best month
March (7.9/10)
Quick decision
Should you visit Koh Samui in September?
✅ Good
✅ Yes if: you're willing to accept showers in exchange for lower prices and fewer tourists.
❌ No if: you're planning 100% outdoor activities — rain is frequent.
Our take: September is a good time to visit Koh Samui. March remains slightly better (+0.8 pts).
By trip type
Koh Samui in September by trip type
- 🏙️ 🏙️ City break / culture : ✅ Good
- 🚶 🚶 Outdoor activities : ⚠️ Possible
- 🏖️ Beach / swimming : ⚠️ Possible
- 💰 💰 Budget : ✅ Low season
Local context
What to expect in September
🎯 Good family period — decent temperatures and sites accessible without crowds Autumn in Koh Samui is often underrated: 30°C, golden light and declining crowds. An interesting window. With 67% of rainy days, always have indoor alternatives planned. Not the best window, but acceptable if dates are constrained. March (7.9/10) is significantly better if possible.
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All months for Koh Samui
Annual table
Month-by-month comparison
| Month | Min °C | Max °C | Rain % | Precip mm | Sun h/d | Score |
|---|---|---|---|---|---|---|
| 🌤️ January | 24°C | 28°C | 57% | 4.3 | 10.9h | 7.6/10 |
| 🌤️ February | 25°C | 29°C | 48% | 2.1 | 11.0h | 7.8/10 |
| 🌤️ March | 26°C | 30°C | 35% | 1.4 | 11.0h | 7.9/10 |
| 🌤️ April | 26°C | 31°C | 49% | 3.6 | 11.2h | 7.4/10 |
| ⛅ May | 26°C | 31°C | 65% | 3.8 | 11.1h | 7.2/10 |
| 🌤️ June | 26°C | 31°C | 54% | 2.5 | 10.9h | 7.3/10 |
| 🌤️ July | 26°C | 31°C | 59% | 3.2 | 10.0h | 7.2/10 |
| 🌤️ August | 26°C | 31°C | 59% | 2.7 | 10.6h | 7.2/10 |
| ⛅ September | 26°C | 30°C | 67% | 4.4 | 10.0h | 7.1/10 |
| 🌧️ October | 25°C | 29°C | 88% | 7.3 | 9.9h | 7.0/10 |
| ⛅ November | 25°C | 28°C | 83% | 9.5 | 10.0h | 7.1/10 |
| ⛅ December | 24°C | 28°C | 63% | 7.2 | 10.5h | 7.4/10 |
Ideal
Fair
Challenging climate
◀ Current month · Source Open-Meteo · 10 years
📊 Data source
Data based on 10 years of ERA5 records via Open-Meteo, with ECMWF seasonal adjustment. In September, Koh Samui averages 30°C, 67% rainy days and 10.0h of sunshine per day. Overall weather score: 7.1/10.
See methodology →
Comparison
September vs March (best month)
The best month is March (score 7.9/10). Difference:
- 🌡️ Max temperature : +0°C
- 🌧 Rainy days : -32%
- ☀️ Sunshine : +1.0h/day
FAQ
FAQ — Koh Samui in September
Is September a good time to visit Koh Samui?
September is an acceptable time for Koh Samui (score 7.1/10). Conditions are decent but not optimal — consider March (7.9/10) if possible.
Does it rain a lot in Koh Samui in September?
Yes, 67% of days see rain in September. Plan some indoor activities as backup.
Accommodation
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Activities & tours
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