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Weather in Ko Samui - 14-day forecast

Detailed weather forecast for Ko Samui, Thailand: daytime and night temperature, rain, sunrise and sunset - today and for the next two weeks.
Forecast for the next days in Ko Samui
today🌧️ 32°💧 0.6 mm
Sun🌧️ 34°💧 1.2 mm
Mon🌧️ 29°💧 0.1 mm
Tue🌧️ 29°💧 1.9 mm
Wed🌧️ 29°💧 0.3 mm
Thu🌧️ 28°💧 3.9 mm
Fri🌧️ 26°💧 11.8 mm
Sat🌧️ 27°💧 9 mm
Forecast vs 1991-2020 climate normal

How does the current forecast compare with normal?

We compare the coming days with weather usually observed at this time of year.

NASA POWER

Saturday 5 Sept in Ko Samui, the forecast high is 32°C. Typical daytime temperatures at this time of year range from 28°C to 29°C, so it will be exceptionally warm. It is warmer than 99% of similar days.

32°Cexceptionally warm
usually 28°C–29°C
warmer than 99% of similar days
night: exceptionally warm rain: exceptionally dry wind: exceptionally strong
34°Cexceptionally warm
usually 28°C–29°C
warmer than 99% of similar days
night: exceptionally warm rain: less rain than usual wind: exceptionally strong
29°Cnear normal
usually 28°C–29°C
night: exceptionally warm rain: exceptionally dry wind: exceptionally strong
29°Cwarmer than usual
usually 28°C–29°C
warmer than 83% of similar days
night: exceptionally warm rain: less rain than usual wind: exceptionally strong
29°Cnear normal
usually 28°C–29°C
night: exceptionally warm rain: exceptionally dry wind: exceptionally strong
28°Ccooler than usual
usually 28°C–29°C
cooler than 87% of similar days
night: exceptionally warm rain: typical rainfall wind: exceptionally strong
26°Cexceptionally cool
usually 28°C–29°C
cooler than 99% of similar days
night: exceptionally cool rain: more rain than usual wind: exceptionally strong

How warm was this week in previous years?

Each bar shows the average daily high during the same 7-day period in each year.

swipe to see more years →
25°30°35° 1981: 29°C1982: 29°C1983: 29°C1984: 28°C1985: 29°C1986: 28°C1987: 30°C1988: 29°C1989: 29°C1990: 29°C1991: 29°C1992: 29°C1993: 28°C1994: 28°C1995: 28°C1996: 28°C1997: 29°C1998: 29°C1999: 28°C2000: 29°C2001: 29°C2002: 29°C2003: 29°C2004: 29°C2005: 29°C2006: 29°C2007: 29°C2008: 28°C2009: 29°C2010: 29°C2011: 29°C2012: 28°C2013: 28°C2014: 29°C2015: 29°C2016: 29°C2017: 30°C2018: 29°C2019: 29°C2020: 29°C2021: 29°C2022: 29°C2023: 29°C2024: 30°C2025: 29°C 2026 forecast: 29°C current forecast 29°C 198119902000201020202026
cooler yearstypical rangewarmer years2026 forecastcurrent forecast

From 1981 to 2025, the 5-11 Sept period averaged 29°C by day. The coolest year was 1984 (28°C) and the warmest was 2024 (30°C). The current forecast averages 29°C - higher than in 93% of historical years.

Historical reference: NASA POWER daily gridded data (MERRA-2), the 1991-2020 normal and a +/- 7-day calendar window. The typical range is the 20th-80th percentile. This is not a city weather-station reading and does not change the current forecast. NASA POWER Daily API.

14-day forecast - Ko Samui

Ko Samui - 14-day weather forecast infographic

Ko Samui 30 & 45-day weather - long-range outlook

Next 16 days · forecast
28°
around 28° at night · days with rain: 13
Weeks 3-4 · avg for September
32°
around 27° at night · rain chance 38%
Weeks 5-7 · avg for October
31°
around 26° at night · rain chance 50%
The 30 & 45-day outlook for Ko Samui: the next 16 days are a numerical forecast updated daily - on average 28° by day and 28° at night. Further out we rely on multi-year climate averages: around 32° in September, and about 31° in October. Forecasts beyond two weeks are indicative only.

Day-by-day forecast for Ko Samui

Saturday5 September 2026
🌧️32°light rain
sunrise 06:11 · sunset 18:27 · night 29° · evening 31° · rain 0.59 mm · humidity 74% · wind 10 m/s · clouds 99%
Sunday6 September 2026
🌧️34°light rain
sunrise 06:11 · sunset 18:26 · night 29° · evening 32° · rain 1.19 mm · humidity 74% · wind 10 m/s · clouds 93%
Monday7 September 2026
🌧️29°light rain
sunrise 06:11 · sunset 18:26 · night 29° · evening 31° · rain 0.11 mm · humidity 74% · wind 11 m/s · clouds 99%
Tuesday8 September 2026
🌧️29°light rain
sunrise 06:11 · sunset 18:25 · night 29° · evening 30° · rain 1.85 mm · humidity 70% · wind 9 m/s · clouds 99%
Wednesday9 September 2026
🌧️29°light rain
sunrise 06:11 · sunset 18:25 · night 28° · evening 29° · rain 0.26 mm · humidity 73% · wind 11 m/s · clouds 100%
Thursday10 September 2026
🌧️28°light rain
sunrise 06:11 · sunset 18:24 · night 28° · evening 27° · rain 3.85 mm · humidity 76% · wind 9 m/s · clouds 100%
Friday11 September 2026
🌧️26°moderate rain
sunrise 06:11 · sunset 18:23 · night 26° · evening 27° · rain 11.76 mm · humidity 89% · wind 10 m/s · clouds 100%
Saturday12 September 2026
🌧️27°moderate rain
sunrise 06:10 · sunset 18:23 · night 28° · evening 27° · rain 9 mm · humidity 78% · wind 11 m/s · clouds 100%
Sunday13 September 2026
🌧️29°light rain
sunrise 06:10 · sunset 18:22 · night 28° · evening 28° · rain 2.34 mm · humidity 72% · wind 12 m/s · clouds 96%
Monday14 September 2026
🌧️28°light rain
sunrise 06:10 · sunset 18:22 · night 29° · evening 29° · rain 5.34 mm · humidity 75% · wind 11 m/s · clouds 99%
Tuesday15 September 2026
🌧️27°light rain
sunrise 06:10 · sunset 18:21 · night 28° · evening 28° · rain 6.36 mm · humidity 82% · wind 9 m/s · clouds 100%
Wednesday16 September 2026
🌧️28°light rain
sunrise 06:10 · sunset 18:20 · night 28° · evening 28° · rain 3.03 mm · humidity 74% · wind 11 m/s · clouds 96%
Thursday17 September 2026
🌧️28°light rain
sunrise 06:10 · sunset 18:20 · night 28° · evening 28° · rain 5.43 mm · humidity 75% · wind 12 m/s · clouds 99%
Friday18 September 2026
🌧️27°moderate rain
sunrise 06:10 · sunset 18:19 · night 27° · evening 27° · rain 10.23 mm · humidity 83% · wind 13 m/s · clouds 100%
Saturday19 September 2026
🌧️26°light rain
sunrise 06:10 · sunset 18:19 · night 27° · evening 28° · rain 8.37 mm · humidity 86% · wind 16 m/s · clouds 100%
Sunday20 September 2026
🌧️28°light rain
sunrise 06:10 · sunset 18:18 · night 28° · evening 29° · rain 5.64 mm · humidity 78% · wind 14 m/s · clouds 100%

UV index in Ko Samui - is it safe to sunbathe?

UV INDEX · 16-DAY FORECASTKo Samui03681111+9UV VERY HIGHtoday, daily maxSPF 50, long sleeves and shade between 10:00 and16:00.Unprotected fair skin may burn in about 20 min9Sat5.099Sun6.099Mon7.099Tue8.098Wed9.098Thu10.093Fri11.091Sat12.094Sun13.097Mon14.098Tue15.099Wed16.099Thu17.099Fri18.098Sat19.097Sun20.090-2 low3-5 moderate6-7 high8-10 very high11+ extremeworld-prices.com · 2026-09-05
Today the UV index in Ko Samui is 9 (very high) - unprotected fair skin can burn in about 20 minutes. SPF 50, long sleeves and shade between 10:00 and 16:00.

Sea temperature - Ko Samui

Water today
31°C
Week avg
30°C
Waves today
0.2 m
How's the water?
very warm
16-day sea temperature forecast:
5.09 31°C6.09 31°C7.09 31°C8.09 31°C9.09 30°C10.09 30°C11.09 30°C12.09 30°C13.09 30°C
Average sea temperature through the year:
Jan 29°CFeb 29°CMar 30°CApr 32°CMay 32°CJun 31°CJul 31°CAug 31°CSep 30°COct 31°CNov 30°CDec 29°C
Sea-surface temperature from marine models, updated daily. See also: where the sea is warmest right now.

Ko Samui weather through the year

Ko Samui - annual climate

Warmest, driest months on average: January, February, December.

Upcoming public holidays in Thailand: King Bhumibol Memorial Day — 13 October · Chulalongkorn Day — 23 October · King Bhumibol's Birthday, National Day and Father's Day — 7 December. Full calendar and travel notes

Nearby and related places

PhitsanulokKo Pha NganPhuketKo ChangSamut PrakanChiang Rai

FAQ - Ko Samui weather

What is the weather like in Ko Samui today?
Today it is about 32° during the day and 29° at night, light rain.
How far ahead can I check the forecast for Ko Samui?
This page shows a detailed 14-day forecast plus the long-term monthly climate, so you can plan both a short trip and a holiday months ahead.