Weather in Koh Samui in September
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Compare car hire prices → Affiliate link — we earn a commission at no extra cost to youSeptember in Koh Samui is hot, with average highs of 29.2°C and lows of 25.4°C. It is very wet, with around 22 rainy days, with roughly 8.5 hours of sunshine a day. Weather-wise, this is one of the most reliable months to travel. For the complete picture, see the best time to visit Koh Samui — every month compared. Once you know when to go, find your Koh Samui packing list at 247PackingList.
Get ready for Koh Samui in September
Search flights to Koh Samui
Compare 100+ airlines for September — one search, best price.
Search Flights →Lightweight travel clothing
Lightweight, breathable clothing and a compact travel umbrella are essential in this climate.
Check Price →What to pack for Koh Samui in September
- Light layers
- Sunscreen
- T-shirts and light trousers or shorts
- Compact travel umbrella
- Waterproof jacket
- Quick-dry clothing
Compare all months in Koh Samui
| Month | High | Rain | Rating |
|---|---|---|---|
| January | 28.5°C | 43.1mm | 10/10 |
| February | 29.0°C | 58.2mm | 10/10 |
| March | 30.5°C | 36.5mm | 10/10 |
| April | 31.1°C | 106.9mm | 9/10 |
| May | 31.0°C | 134.5mm | 9/10 |
| June | 30.6°C | 102.4mm | 9/10 |
| July | 30.0°C | 149.9mm | 9/10 |
| August | 30.4°C | 114.2mm | 9/10 |
| September | 29.2°C | 196.8mm | 9/10 |
| October | 28.5°C | 244.4mm | 8/10 |
| November | 28.1°C | 323.1mm | 8/10 |
| December | 27.9°C | 161.7mm | 9/10 |
Full month-by-month guide: best time to visit Koh Samui →
For facts about Thailand — currency, language and dialling code — see our Thailand country guide at 247CountryInfo. Travellers also find it useful to keep a Koh Samui travel guide to hand. Check clothing sizes in Thailand before you shop.
Frequently Asked Questions
Is September a good time to visit Koh Samui?
September rates 9/10 for visiting Koh Samui — excellent time to visit. Expect average highs of 29.2°C, 196.8mm of rain across the month and about 8.5 hours of daily sunshine.
What is the temperature in Koh Samui in September?
In September, Koh Samui has average highs of 29.2°C (84.6°F) and average lows of 25.4°C (77.7°F).
Does it rain in Koh Samui in September?
Yes — September is one of the wetter months in Koh Samui, averaging 196.8mm of rain over roughly 22 rainy days. Pack for heavy showers.
What should I wear in Koh Samui in September?
For Koh Samui in September (29.2°C highs / 25.4°C lows), pack light layers plus sunscreen, t-shirts and light trousers or shorts, compact travel umbrella.
More essentials for Koh Samui in September
Packing cubes
Keep the bag organised whatever the weather — compression cubes for every size.
Check Price →Travel first aid kit
Compact TSA-friendly kit for peace of mind wherever you travel.
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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.