The month in detail
What to expect in September
In September, Koh Samui sees 30°C during the day with 4.8h of sunshine per day. Expect rain on 35% of days — a light raincoat in the bag is recommended.
September ranks 8 out of 12 months in Koh Samui.
This month's conditions
What it's like in September
UV index
8 · high
sunscreen and hat advised
Feels like
very humid
24°
Sea
30°C
warm, ideal
Daylight
12.0h of daylight
Air quality
good
AQI 20
Compare
Is September the right month?
The best month in Koh Samui is February (6.0/10), 0.9 pt higher than September.
Book
Plan your trip
Hotels at their lowest outside peak season, highest on comfortable months. Shoulder seasons offer a good price/climate compromise.
Stay
Hotels & rentals · Koh Samui
Expedia →
Activities
Tours, tickets, experiences
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Flights
Multi-airline comparator
Kiwi →
🎟️ Activities & tours · Koh Samui
GetYourGuide selection · free cancellation
Practical info
What you need to know before you go
Three angles: the country (language, currency, safety, budget), the year-round climate, and the specifics of a tropical stay.
Country · Thailand
🗣️LanguageThai
💶CurrencyThai Baht (฿)
🚗DrivingLeft-hand
🛡️Safety ⓘSafe · 2/5
💰Cost of living ⓘCheap · 2/5
🌡️ Climate
🌍Climate typeEquatorial tropical
📈Climate trend ⓘStable
🔥Hottest monthApril · 31°C
❄️Coolest monthJanuary · 28°C
🌧️Rainiest month ⓘNovember · 55%
🏝️ Tropical stay
🌞Dry season ⓘMay → Sep
🌧️Wet season ⓘDec → Mar
🌀Cyclones ⓘNone (equator)
Explore
Other destinations in September
If September doesn't convince you for this destination, compare with others.
Location
Where is Koh Samui ?
Global position + regional geographic context.
🌍 World
🔍 Geographic context
ThailandEquatorial tropical climate with a 6.0 → 4.9 gap between best and worst month. 10 years of ERA5 data to choose by project.
9.51°N · 100.06°E
Questions
Frequently asked questions
What is the best time to visit Koh Samui?
February is the best month with 29.0°C highs, 25.0°C lows, 7.6h of sunshine and 15.0% rainy days.
How many hours of sunshine does Koh Samui get in February?
Koh Samui averages 7.6 sunshine hours per day in February. It is the sunniest month with a climate score of 5.9/10.
What is the rainiest month in Koh Samui?
October is the most unfavourable month with October has the lowest climate score of the year and the lowest climate score of the year.
What are the temperatures at night in Koh Samui in February?
In February, overnight lows reach 25.0°C, while afternoon highs average 29.0°C.
Is Koh Samui good in winter?
In winter (December-February), Koh Samui scores 5.5/10 on average — Decent period conditions for cultural visits.. The best month overall remains February with a score of 5.9/10.
When should you avoid Koh Samui?
October is the most difficult month to visit Koh Samui, with October has the lowest climate score of the year. Climate conditions are at their lowest of the year during this period.
Can you swim in Koh Samui in September?
In September, the sea averages 30°C in Koh Samui: warm, ideal. Ideal conditions for swimming and snorkeling.
Do you need sun protection in Koh Samui in September?
The average UV index reaches 8 in September in Koh Samui (high), with about 12.0h of daylight. Sunscreen and hat advised.