Ko Samui climate — normals and trends
Ko Samui (Thailand) has a tropical monsoon climate (Am) under the Köppen-Geiger classification. Its mean annual temperature is 27.2 °C and it receives 1,613 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is May (28.1 °C on average) and the coldest is January (26.2 °C). Rainfall peaks in November.
Ko Samui averages 0 frost days, 13 hot days (≥ 30 °C) and 213 rainy days per year.
Ko Samui has warmed by +1.0 °C between 1940 and 2025, or +0.12 °C per decade. This trend is statistically significant.
The hottest day of the period reached 32.1 °C (on 20 May 2004) and the coldest 22.6 °C (on 24 December 1999).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
Ko SamuiSurat Thani
- coords
- 9.54°, 99.94°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
27.2°C
Average daily high
28.0°C
Average daily low
26.4°C
Annual rainfall
1,613mm
Sunshine / day
10.1h
Mean relative humidity
80%
Average peak wind
22.0km/h
Seasonal range
1.9°C
Frost days (< 0 °C)
0 d/yr
Hot days (≥ 30 °C)
13 d/yr
Rainy days (≥ 1 mm)
213 d/yr
Annual snowfall
0.0 cm
Average feels-like high
32.5 °C
Average feels-like low
29.4 °C
Average peak gust
32.4 km/h
Tropical nights (≥ 20 °C)
365 d/yr
Solar radiation
19.8 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.0 °C
since 1940
+0.1 °C per decade · r² = 0.69 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
32.1 °C
20 May 2004
Coldest day
22.6 °C
24 December 1999
Wettest day
208 mm
27 January 1953
Windiest day
65.9 km/h
26 October 1962
Strongest gust
94.0 km/h
26 October 1962
Hottest feels-like
40.4 °C
27 May 2024
Coldest feels-like
20.4 °C
24 December 1999
Sunniest day
12.6 h
19 June 1940
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 27.1 °C | +0.3 °C | 31 mm | -41 mm |
| Feb | 27.4 °C | +0.2 °C | 132 mm | +84 mm |
| Mar | 28.3 °C | +0.3 °C | 64 mm | -3 mm |
| Apr | 29.0 °C | +0.2 °C | 191 mm | +95 mm |
| May | 29.2 °C | +0.1 °C | 193 mm | +66 mm |
| Jun | 29.4 °C | +0.3 °C | 72 mm | -19 mm |
| Jul | 29.6 °C | +0.9 °C | 54 mm | -41 mm |
| Aug | 28.8 °C | +0.3 °C | 92 mm | -9 mm |
| Sep | 28.6 °C | +0.6 °C | 99 mm | -50 mm |
| Oct | 28.1 °C | +0.5 °C | 364 mm | +71 mm |
| Nov | 27.6 °C | +0.3 °C | 243 mm | -75 mm |
| Dec | 27.3 °C | +0.3 °C | 96 mm | -63 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of Ko Samui?
Ko Samui has a tropical monsoon climate (Köppen Am). Over 1940-2025, the average annual temperature is 27.2 °C and it receives 1,613 mm of precipitation per year.
What is the hottest day ever recorded in Ko Samui?
The hottest day measured in Ko Samui between 1940 and 2025 was 20 May 2004, reaching 32.1 °C.
What is the coldest day in Ko Samui?
The coldest day measured in Ko Samui between 1940 and 2025 was 24 December 1999, at 22.6 °C.
Does it snow in Ko Samui?
Almost never: Ko Samui sees virtually no snow, with about 0 frost days per year.
Has the climate of Ko Samui warmed?
Yes: Ko Samui warmed by +1.0 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Ko Samui?
The wettest day measured in Ko Samui between 1940 and 2025 was 27 January 1953, with 208 mm of rain in 24 hours.
What was the windiest day in Ko Samui?
The windiest day measured in Ko Samui between 1940 and 2025 was 26 October 1962, with winds reaching 65.9 km/h.
What is the warmest month in Ko Samui?
The warmest month in Ko Samui is May (28.1 °C on average); the coldest is January (26.2 °C).
How much does it rain in Ko Samui?
Ko Samui receives on average 1,613 mm of precipitation per year, spread over about 213 rainy days.
Is it sunny in Ko Samui?
Ko Samui gets on average 10.1 hours of sunshine per day, roughly 3,687 hours per year over 1940-2025.
Are there tropical nights in Ko Samui?
Yes: Ko Samui has on average 365 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Ko Samui?
In Ko Samui, between 1940 and 2025, the highest apparent temperature reached 40.4 °C on 27 May 2024, and the lowest was 20.4 °C on 24 December 1999.
Compare Ko Samui with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Ko Samui