Koh Samui weather in September
Monthly temperatures, rain, humidity, what to wear and what to pack — 2024–2025 historical average
Koh Samui September weather at a glance
In September, Koh Samui averages 24.8°C, with typical highs of 27.5°C and lows of 22.7°C. The historical average is 21 wet days and 78% humidity.
Koh Samui September temperature & humidity
Koh Samui September rain & wet days
Pack a light rain jacket, waterproof pouch and quick-dry shoes. Keep an indoor stop available between outdoor activities.
What to wear in Koh Samui in September
Choose breathable summer clothes and pack sun protection. Rain is frequent at roughly 21 days in the month; pack a rain jacket and water-resistant shoes.
- DaytimeBreathable short sleeves, hat and sunscreen · average high 27.5°C
- Morning & eveningLight layer for air-conditioned rooms · average low 22.7°C
- FootwearComfortable walking shoes; quick-dry footwear for rainy days.
Packing essentials
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Koh Samui September sunrise & sunset times
2026 September · Local time (Asia/Bangkok)
| Date | Sunrise | Sunset | Daylight |
|---|---|---|---|
| 2026-09-01 | 06:11 | 18:29 | 12h 18m |
| 2026-09-15 | 06:10 | 18:21 | 12h 11m |
| 2026-09-30 | 06:09 | 18:11 | 12h 3m |
For sunset photos, arrive before the listed sunset time. Clouds, mountains and buildings can change when the sun becomes visible or disappears.
Calculated for the city coordinates with daylight saving applied. SunCalc · tz-lookup
Koh Samui travel updates
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Koh Samui rainy season & dry season
Is September wet or dry?
Thailand’s southwest monsoon generally brings rain from mid-May to mid-October. The southern east coast also receives northeast-monsoon rain, so Koh Samui and Phuket do not share one wet/dry-season calendar. The 2024–2025 average for September is 21 wet days.
2024–2025 wet-day averages, not long-term season boundaries. Wet days do not mean all-day rain.
Packing for rainy and dry periods
For rainy periods, bring a light rain jacket, a waterproof pouch and quick-dry clothes. In drier months, pack sunscreen and a hat, plus a compact umbrella for showers. For beach trips, check the boat operator’s weather and cancellation notices.
Season guide: Thailand Government
Koh Samui travel essentials
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Best months to visit Koh Samui
Bar height shows our simple weather-comfort score, not a safety rating; colour shows temperature.
September weather by year
Daily weather in 2025
Daily high and low temperatures; blue labels show precipitation
Frequently asked questions
What is Koh Samui weather like in September?
In September, Koh Samui averages 24.8°C, with typical highs of 27.5°C and lows of 22.7°C. The historical average is 21 wet days and 78% humidity. Our weather-comfort rating for this month is challenging.
Does it rain a lot in Koh Samui in September?
There are about 21 wet days in September. Pack a rain jacket and water-resistant shoes.
What should I wear in Koh Samui in September?
Choose breathable summer clothes and pack sun protection. Rain is frequent at roughly 21 days in the month; pack a rain jacket and water-resistant shoes.
What are the best months to visit Koh Samui?
Recent weather data rates March among the more comfortable months.
Where can I check Koh Samui weather in September in real time?
Check local webcams for the view right now and a local weather service for today’s forecast. Monthly temperatures here are historical averages.
Is September rainy or dry season in Koh Samui?
Thailand’s southwest monsoon generally brings rain from mid-May to mid-October. The southern east coast also receives northeast-monsoon rain, so Koh Samui and Phuket do not share one wet/dry-season calendar. The 2024–2025 average for September is 21 wet days.
Which months have fewer rainy days in Koh Samui?
In our 2024–2025 data, March, April, February have the fewest wet days. These are recent observations, not long-term climate normals. Compare temperatures and your planned activities as well.
What time are sunrise and sunset in Koh Samui in September?
On 2026-09-15, calculated sunrise is 06:10 and sunset is 18:21 in local time (Asia/Bangkok). Times vary by date and terrain.
Koh Samui weather by month
More Southeast Asia destinations in September
Open-Meteo (CC BY 4.0) · 2024–2025 historical data, aggregated and rounded by this site. Not a forecast or long-term climate normal. Calculation method and limitations