AI-generatedKoh Samui at a glance
- Best time
- Jan – Apr
- Warmest month
- May · 30°
- Warmest sea
- May · 30.5°
- Sunshine a year
- 2,300 h
- Rain a year
- 1,712 mm
- Climate
- Tropical
- Time zone
- UTC+7
- Elevation
- 8 m
Climate in Koh Samui
Koh Samui has a tropical climate: it is warm all year round, and the seasons differ mainly in how much rain falls. May is the warmest month with average highs of 30 °C, while January is the coolest at 28 °C. With around 2,300 hours of sunshine a year, Koh Samui is sunny; March is the sunniest month with 8.1 hours a day.
Holiday weather through the year
Weather in October
Holiday weather in October
Good
Best time to visit: January – April
A typical day in October
- Morning, 08:00: about 27°
- Midday, 13:00: about 28°
- Afternoon, 16:00: about 28°
- Evening, 20:00: about 27°
- Night, 23:00: about 27°
06:0818:04
Warm enough for a T-shirt in the evening.
Estimated from the average high and low: coolest around sunrise, warmest in mid-afternoon.
What is the weather like in Koh Samui in October?
In October, Koh Samui is hot: daytime highs average 28 °C, and even at night it stays warm at around 26 °C. The sea averages 29.1 °C – almost as warm as a bath. Expect around 5 hours of sunshine a day. It is the rainy season: rain falls on about 28 days, totalling 288 mm. The air is often humid and muggy. All in all, October is a good month for a holiday in Koh Samui.
More details for October
- Daylight
- 11 h 56 min06:08 – 18:04
- UV index
- 12 · extremeclear sky, noon (estimate)All months
- Muggy days
- 31 daysdew point 18 °C or more
- Wind
- 13 km/haverage daily peak
- Cloud cover
- 85 %on average
- Hot days
- 0 days30 °C or more
- Time zone
- UTC+7Asia/Bangkok
How the score comes together
- Temperatureweight 35 %100 %
- Seaweight 25 %100 %
- Sunshineweight 20 %33 %
- Few rainy daysweight 20 %0 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in October
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
- Insect repellent
- Rain jacket or umbrella
Sea temperature in Koh Samui
Monthly sea surface temperature with the range of cooler and warmer years.
8 in 10 years: 28.6 – 29.6 °C
Swimming season: All year
- cold
- fresh
- refreshing
- pleasant
- warm
- very warm
The sea temperature in Koh Samui ranges from 27.7 °C in January to 30.5 °C in May. At 20 °C and more, the sea is warm enough for swimming all year round.
From April to June and from September to January the sea is even warmer than the afternoon air. The sea temperature varies from year to year: in May, eight out of ten years were between 29.8 and 31.3 °C.
| Month | Average | Cool year | Warm year | Feels |
|---|---|---|---|---|
| JanuaryJan | 27.7° | 27.0° | 28.7° | warm |
| FebruaryFeb | 28.2° | 27.6° | 28.8° | warm |
| MarchMar | 29.1° | 28.5° | 29.6° | very warm |
| AprilApr | 30.2° | 29.6° | 30.8° | very warm |
| MayMay | 30.5° | 29.8° | 31.3° | very warm |
| JuneJun | 30.0° | 29.5° | 30.6° | very warm |
| JulyJul | 29.6° | 29.2° | 30.0° | very warm |
| AugustAug | 29.4° | 28.9° | 29.9° | very warm |
| SeptemberSep | 29.3° | 28.9° | 29.9° | very warm |
| OctoberOct | 29.1° | 28.6° | 29.6° | very warm |
| NovemberNov | 28.7° | 28.0° | 29.4° | warm |
| DecemberDec | 27.9° | 27.1° | 28.7° | warm |
Sunshine hours in Koh Samui
Average hours of bright sunshine per day, next to the length of the day. Tap a month to select it.
In October, the sun shines for about 5.0 of 11.9 hours of daylight in Koh Samui, 42 % of the day.
Sunshine hours: estimated from radiation data (ERA5, 1996–2025) and calibrated against measured station values; no weather station is close enough here. Daylight is the time from sunrise to sunset on the 15th of the month.
UV index in Koh Samui
How strong the sun is at noon, month by month, and how quickly unprotected skin burns.
- Clear-sky UV in October
- 12 · extremeAvoid the midday sun; SPF 50+, covering clothes, hat and sunglasses.
The sun is strongest in April (UV 13).
Minutes until sunburn in October
- Very fair skin
- about 10 min
- Fair skin
- about 15 min
- Light brown skin
- about 20 min
- Olive skin
- about 25 min
Rough guide for unprotected skin at noon under a clear sky; clouds lengthen it, water, sand and snow shorten it. Sunscreen extends the time only partly.
Monthly values: clear-sky noon estimate from the sun's angle, ozone and altitude. UV today: Open-Meteo forecast.
Rain in Koh Samui: rainy days and rainfall
A rainy day is a day with at least 1 mm of rain or snow; the amount is what falls in the whole month. Tap a month to select it.
In October, Koh Samui has about 28 rainy days with 288 mm of rain in total.
Climate through the year
Long-term monthly averages. Tap a month to see its details.
Temperatures through the year
Average daytime high, night-time low and sea temperature per month.
| Month | Score | Day | Night | Sea | Sun | Rain days | Rain mm |
|---|---|---|---|---|---|---|---|
| JanuaryJan | 83 | 28° | 26° | 27.7° | 6.7 h | 10 | 68 |
| FebruaryFeb | 93 | 28° | 26° | 28.2° | 7.8 h | 6 | 38 |
| MarchMar | 90 | 29° | 27° | 29.1° | 8.1 h | 9 | 77 |
| AprilApr | 82 | 30° | 28° | 30.2° | 7.9 h | 14 | 109 |
| MayMay | 72 | 30° | 28° | 30.5° | 6.6 h | 24 | 143 |
| JuneJun | 70 | 30° | 27° | 30.0° | 6.1 h | 21 | 112 |
| JulyJul | 69 | 30° | 27° | 29.6° | 5.7 h | 21 | 117 |
| AugustAug | 69 | 30° | 27° | 29.4° | 5.8 h | 21 | 124 |
| SeptemberSep | 68 | 29° | 27° | 29.3° | 5.3 h | 25 | 173 |
| OctoberOct | 67 | 28° | 26° | 29.1° | 5.0 h | 28 | 288 |
| NovemberNov | 66 | 28° | 26° | 28.7° | 4.9 h | 24 | 298 |
| DecemberDec | 71 | 28° | 26° | 27.9° | 5.8 h | 17 | 165 |
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0)
9.54° N, 99.94° E · 8 m · Asia/Bangkok
Best time to visit Koh Samui
The best time to visit Koh Samui is from January to April. For a beach holiday with the sea above 21 °C, go from January to March. For sightseeing, day trips and hiking, conditions are most comfortable in January. Rain is most frequent from April to December; the wettest month is November with 298 mm.
Koh Samui through the seasons
How the weather changes over the seasons, with averages for each.
Koh Samui in the dry season
Jan – Mar
Excellent
- 28–29 °C by day
- Sea 28 °C
- 8 h of sun a day
- 25 rainy days in all
Koh Samui in the rainy season
Apr – Dec
Good
- 28–30 °C by day
- Sea 29 °C
- 6 h of sun a day
- 194 rainy days in all
Find your perfect month
Tell us what you like and we rate every month in Koh Samui for you.
Your best months: January – March
Based on the climate averages; tap a month to see its details.
Which month for what?
Beach & swimming
Jan – Mar
Sea from 21 °C, warm and mostly dry
Sightseeing & hiking
Jan
15–28 °C and not too much rain
Rainy months
Apr – Dec
12 or more rainy days
Koh Samui month by month
The typical weather for every month at a glance.
83January28° · Sea 28° · 7 h
In January, Koh Samui is hot: daytime highs average 28 °C, and even at night it stays warm at around 26 °C. The sea averages 27.7 °C – lovely and warm for swimming. The sun shines for around 7 hours a day. Rain is frequent, with about 10 rainy days and 68 mm in total. The air is often humid and muggy. All in all, January is an excellent month for a holiday in Koh Samui.
Koh Samui in January93February28° · Sea 28° · 8 h
In February, Koh Samui is hot: daytime highs average 28 °C, and even at night it stays warm at around 26 °C. The sea averages 28.2 °C – lovely and warm for swimming. The sun shines for around 8 hours a day. Rain falls on about 6 days, adding up to 38 mm. The air is often humid and muggy. All in all, February is an excellent month for a holiday in Koh Samui.
Koh Samui in February90March29° · Sea 29° · 8 h
In March, Koh Samui is hot: daytime highs average 29 °C, and even at night it stays warm at around 27 °C. The sea averages 29.1 °C – almost as warm as a bath. The sun shines for around 8 hours a day. Rain falls on about 9 days, adding up to 77 mm. The air is often humid and muggy. All in all, March is an excellent month for a holiday in Koh Samui.
Koh Samui in March82April30° · Sea 30° · 8 h
In April, Koh Samui is hot: daytime highs average 30 °C, and even at night it stays warm at around 28 °C. The sea averages 30.2 °C – almost as warm as a bath. The sun shines for around 8 hours a day. Rain is frequent, with about 14 rainy days and 109 mm in total. On about 15 days the thermometer climbs to 30 °C or more. The air is often humid and muggy. All in all, April is an excellent month for a holiday in Koh Samui.
Koh Samui in April72May30° · Sea 31° · 7 h
In May, Koh Samui is hot: daytime highs average 30 °C, and even at night it stays warm at around 28 °C. The sea averages 30.5 °C – almost as warm as a bath. The sun shines for around 7 hours a day. It is the rainy season: rain falls on about 24 days, totalling 143 mm. On about 16 days the thermometer climbs to 30 °C or more. The air is often humid and muggy. All in all, May is a good month for a holiday in Koh Samui.
Koh Samui in May70June30° · Sea 30° · 6 h
In June, Koh Samui is hot: daytime highs average 30 °C, and even at night it stays warm at around 27 °C. The sea averages 30.0 °C – almost as warm as a bath. Expect around 6 hours of sunshine a day. It is the rainy season: rain falls on about 21 days, totalling 112 mm. On about 14 days the thermometer climbs to 30 °C or more. The air is often humid and muggy. All in all, June is a good month for a holiday in Koh Samui.
Koh Samui in June69July30° · Sea 30° · 6 h
In July, Koh Samui is hot: daytime highs average 30 °C, and even at night it stays warm at around 27 °C. The sea averages 29.6 °C – almost as warm as a bath. Expect around 6 hours of sunshine a day. It is the rainy season: rain falls on about 21 days, totalling 117 mm. On about 9 days the thermometer climbs to 30 °C or more. The air is often humid and muggy. All in all, July is a good month for a holiday in Koh Samui.
Koh Samui in July69August30° · Sea 29° · 6 h
In August, Koh Samui is hot: daytime highs average 30 °C, and even at night it stays warm at around 27 °C. The sea averages 29.4 °C – almost as warm as a bath. Expect around 6 hours of sunshine a day. It is the rainy season: rain falls on about 21 days, totalling 124 mm. On about 9 days the thermometer climbs to 30 °C or more. The air is often humid and muggy. All in all, August is a good month for a holiday in Koh Samui.
Koh Samui in August68September29° · Sea 29° · 5 h
In September, Koh Samui is hot: daytime highs average 29 °C, and even at night it stays warm at around 27 °C. The sea averages 29.3 °C – almost as warm as a bath. Expect around 5 hours of sunshine a day. It is the rainy season: rain falls on about 25 days, totalling 173 mm. The air is often humid and muggy. All in all, September is a good month for a holiday in Koh Samui.
Koh Samui in September67October28° · Sea 29° · 5 h
In October, Koh Samui is hot: daytime highs average 28 °C, and even at night it stays warm at around 26 °C. The sea averages 29.1 °C – almost as warm as a bath. Expect around 5 hours of sunshine a day. It is the rainy season: rain falls on about 28 days, totalling 288 mm. The air is often humid and muggy. All in all, October is a good month for a holiday in Koh Samui.
Koh Samui in October66November28° · Sea 29° · 5 h
In November, Koh Samui is hot: daytime highs average 28 °C, and even at night it stays warm at around 26 °C. The sea averages 28.7 °C – lovely and warm for swimming. Expect around 5 hours of sunshine a day. It is the rainy season: rain falls on about 24 days, totalling 298 mm. The air is often humid and muggy. All in all, November is a good month for a holiday in Koh Samui.
Koh Samui in November71December28° · Sea 28° · 6 h
In December, Koh Samui is hot: daytime highs average 28 °C, and even at night it stays warm at around 26 °C. The sea averages 27.9 °C – lovely and warm for swimming. Expect around 6 hours of sunshine a day. It is the rainy season: rain falls on about 17 days, totalling 165 mm. The air is often humid and muggy. All in all, December is a good month for a holiday in Koh Samui.
Koh Samui in DecemberKoh Samui compared
Put Koh Samui side by side with another destination.
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Koh Samui vs. Ao Nang
In October the holiday weather in Koh Samui and Ao Nang is about equally good (score 67 vs. 64). During the day it is about as warm in Ao Nang as in Koh Samui. The sea is about equally warm. Ao Nang gets one hour less sunshine a day.
| in October | Koh Samui | Ao Nang |
|---|---|---|
| Holiday score | 67 | 64 |
| Daytime high | 28° | 28° |
| Sea | 29° | 29° |
| Sunshine | 5 h | 4 h |
| Rainy days | 28 | 28 |
| Best time | Jan – Apr | Jan – Mar |
Through the year
Thailand in October: the best places
In October, Koh Samui ranks 1 of 8 destinations in this country.
- Koh SamuiThis page28°29°67
- 2Hua Hin29°29°67
- 3Pattaya30°30°67
- 4Ao Nang28°29°64
- 5Khao Lak28°29°64
- 6Patong28°29°64
- 7Chiang Mai29°52
- 8Bangkok31°34
Planning a trip to Koh Samui
Weather for your travel dates
Pick your arrival and length of stay, and we sum up the weather to expect.
Getting there
Flying from
- Nonstop flight
- about 12 h 25 min
- Distance
- 9,890 km
- Time zone
- UTC+7
Most routes need a change of planes, which adds time.
Estimated from the straight-line distance: 30 minutes for take-off and landing plus 830 km/h cruising speed.
Frequently asked questions about Koh Samui
When is the best time to visit Koh Samui?
The best time to visit Koh Samui is from January to April. That is when the holiday weather score, which combines temperature, sea, sunshine and rain, is highest.
How warm is the sea in Koh Samui?
The sea temperature in Koh Samui ranges from 27.7 °C in January to 30.5 °C in May. At 20 °C and more, the sea is warm enough for swimming all year round.
Can you swim in Koh Samui in October?
Yes. In October the sea averages 29.1 °C – almost as warm as a bath.
What is the warmest month in Koh Samui?
May is the warmest month, with average highs of 30 °C and nights around 28 °C. January is the coolest month at 28 °C.
When does it rain most in Koh Samui?
Rain is most frequent from April to December; the wettest month is November with 298 mm. The driest month is February with 38 mm.
How many hours of sunshine does Koh Samui get?
Koh Samui gets around 2,300 hours of sunshine a year. The sunniest month is March with 8.1 hours a day; in November there are 4.9 hours a day.
What time zone is Koh Samui in?
Koh Samui uses the time zone Asia/Bangkok, at UTC+7 all year.
How long is the flight from London to Koh Samui?
A nonstop flight from London to Koh Samui takes about 12 h 25 min, for a straight-line distance of about 9,890 km. Most routes need a change of planes, which adds time.
Near Koh Samui
Other destinations close by.
Places with a climate like Koh Samui
Destinations whose weather through the year is closest to Koh Samui's – good alternatives.