Weather by month
Koh Samui in September 2027
September on Koh Samui usually mixes sunny spells with showers. Rain often comes in short bursts, so most days still have time for the beach.
September at a glance
- Average high
- 31.9 °C
- Average low
- 24.8 °C
- Rainfall
- 118 mm
- Rain days
- 10.6 days
29% less rain than an average month
Averages: WMO Climate Normals 1991–2020, Ko Samui (station 48550, Thai Meteorological Department observations), as published on Wikipedia (secondary source, checked 7 Nov 2026). Not a forecast — for warnings use the Thai Meteorological Department. TMD weather warnings
Season verdict
Mixed — sunny spells and showers; good for most plans with a flexible day.
Good for
Beach mornings, temples and markets, spa and cooking classes, flexible boat trips
Less good for
Fixed-date boat trips without a backup day
Sea & boat trips
Outside the northeast monsoon the sea is calmer more often, but wind and waves still change day to day. Always check the operator before a boat trip.
Open or closed
Ang Thong Marine National Park is usually open in September. Trips still depend on the sea on the day. Park information
Holidays & alcohol-sale bans in September 2027
No Thai holidays from our list fall in September 2027.
Full holiday calendar · Dates: Bank of Thailand holiday notifications and Thai press; check before you travel.
Events in September
No dated events are listed for September yet.
What to pack
Sun protection plus a light rain jacket or poncho, and a dry bag for boat days.
One next step
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