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Climate · Koh Samui

Koh Samui in September

Warm and wet, as the days shorten.

Typical weather, averaged over 30 years

September in Koh Samui is warm: highs near 82°F, lows near 77°F. Rain falls on about six days a week, and the days shorten by 11 minutes from the first week to the last.September in Koh Samui is warm: highs near 28°C, lows near 25°C. Rain falls on about six days a week, and the days shorten by 11 minutes from the first week to the last.

High
82°F28°Caverage
Low
77°F25°Caverage
Wet days
6a week · 80% of days
Daylight
12h 09mon average

Is September a good time to visit Koh Samui?

September sits outside Koh Samui's best months, which run from January to March. Expect warm days and rain on about six days a week.

How we judge it: every month is scored on how close its typical high comes to the range from 70°F to 80°F, how mild its nights are, and how rarely it rains. The best months are the run of months that scores best.How we judge it: every month is scored on how close its typical high comes to the range from 21°C to 27°C, how mild its nights are, and how rarely it rains. The best months are the run of months that scores best.

How September sits in the year

week by week

Temperature

Highs near 82°F in September, against 80°F to 84°F through the year.Highs near 28°C in September, against 27°C to 29°C through the year.

Chance of a wet day

80% of days in September, against 30% to 89% through the year.

Cloud cover

79% cover in September, against 59% to 80% through the year.

Daylight

12h 09m in September, against 11h 35m to 12h 40m through the year.

Week by week, lightly smoothed, with September shaded. The olive line marks the best months. Hover or tap a week for its figures.

Either side

  1. August83°28°low 77°low 25°4 wet days a weekRain on about four days a week.
  2. September82°28°low 77°low 25°6 wet days a weekRain on about six days a week.
  3. October81°27°low 76°low 24°6 wet days a weekRain on about six days a week.

Where Koh Samui sits, in September

Asia/Bangkok
this place
typical high in September 40°F4°C95°F35°C
Sunrise, mid-September
6:10 AMsets 6:21 PM
Above the sea
420 mlow-lying
Latitude
9.5°Nnorthern hemisphere
Nearest of ours
Krabi183 km south-west

The land around Koh Samui, shaded by its typical high in September, the planning map's own layer. Hover the map for the figure at that spot; tap it on a phone. Clock times are local, for the 15th.

Elsewhere in Thailand in September

high · low · wet days
See September on the planning mapThe whole year in Koh Samui

Typical weather, averaged over 30 years (1995–2024), from the 11 km grid square nearest Koh Samui. Temperatures are adjusted against 66 weather stations: daytime highs read about 3.1°F cold in the source data and are raised to match, and both highs and lows are adjusted for the town's height (420 m) against the climate model's (71 m).Temperatures are adjusted against 66 weather stations: daytime highs read about 1.7°C cold in the source data and are raised to match, and both highs and lows are adjusted for the town's height (420 m) against the climate model's (71 m). Daylight is calculated from latitude. Charts are lightly smoothed week to week; the figures in the table are not. Source: Copernicus ERA5-Land reanalysis; cloud cover from NASA's MERRA-2 reanalysis, on a coarser grid of about 50 km. Contains modified Copernicus Climate Change Service information 2026; neither the European Commission nor ECMWF is responsible for any use of it. These are averages, not a forecast.

Daylight is calculated from latitude. Charts are lightly smoothed week to week; the figures in the table are not.

Source: Copernicus ERA5-Land reanalysis; cloud cover from NASA's MERRA-2 reanalysis, on a coarser grid of about 50 km. Contains modified Copernicus Climate Change Service information 2026; neither the European Commission nor ECMWF is responsible for any use of it. These are averages, not a forecast.