Ko Samui weather in January

In January, Ko Samui sees average daytime highs of 27°C and overnight lows near 26°C, with 76 mm of rain across 9.4 wet days and about 11.5 hours of daylight. It is the 12th-warmest and 11th-wettest month of the year here.

Day-to-day highs hold fairly steady near 27°C through the month. The sky is clear or mostly clear about 36% of the time in January, and the air most often feels oppressive.

Daylight stretches from about 11 h 30 min at the start of January to 11 h 36 min by month's end. Set against the rest of the year, January is Ko Samui's 3rd-clearest and 6th-windiest month. For the whole year in context, see Ko Samui's year-round climate.

Daytime high
27°
12th warmest
Overnight low
26°
1st coldest
Rainfall
76 mm
9.4 wet days
Daylight
11 h 30 min
6:45 AM – 6:15 PM
Cloud cover
55%
3rd clearest
Wind
17 km/h
6th windiest
Solar energy
5.2 kWh/m²
Travel score
6.7
out of 10

Ko Samui is city in Surat Thani province, Thailand.

Density
219/km²
people per km²
Founded
1956

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in January

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 27°C through the month.

A typical January day in Ko Samui reaches about 27°C in the afternoon and slips back to 26°C overnight — a 1°C spread between the day's warmth and the night's chill. On most days the high lands between 26°C and 28°C. Set against its neighbours, January runs on par with December and on par with February.

20°23°25°28°30°151015202531
Avg high (°C)Avg low (°C)
12726
22726
32726
42726
52726
62726
72726
82726
92726
102726
112726
122726
132726
142726
152726
162726
172726
182726
192726
202726
212726
222726
232726
242726
252726
262726
272726
282726
292726
302726
312726

How January really feels in Ko Samui

Once humidity and wind are folded in, January averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

January sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Ko Samui weather by month

How January compares with the rest of the year at a glance. January is the 12th-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan27° / 26°769.411.56.7
Feb27° / 26°355.311.77.3
Mar28° / 27°888.411.96.4
Apr29° / 28°9511.712.25.3
May29° / 27°11621.212.43.8
Jun29° / 27°8918.812.53.9
Jul29° / 27°8418.412.54.2
Aug29° / 27°911812.34.3
Sep28° / 27°14022.812.13.9
Oct28° / 26°2862611.83.9
Nov28° / 26°28920.911.64.6
Dec27° / 26°14513.211.55.9

Cloud cover in January

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 36% of the time in January.

Beyond those clear spells, partly cloudy skies cover about 19% of January, with mostly cloudy or overcast conditions the remaining 45%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15050
25050
35050
45149
55149
65248
75347
85248
95347
105446
115347
125446
135347
145446
155446
165446
175446
185446
195446
205644
215644
225644
235644
245842
255842
265941
276040
286040
296139
306238
316238

Chance of precipitation in January

Any precipitation

Ko Samui gets around 76 mm of rain over 9.4 wet days in January. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 30% and peaks near 34% on the wettest days. The odds ease toward the end of the month.

0%10%20%30%40%151015202531
Rain chance (%)
134
234
334
434
534
633
733
833
932
1031
1131
1230
1330
1429
1529
1629
1729
1829
1929
2029
2129
2229
2329
2428
2528
2628
2728
2827
2927
3026
3125

Humidity in January

DryComfortableHumidMuggyOppressiveMiserable

Most of January feels oppressive — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, January lands in the oppressive band about 82% of days. Sticky, muggy-or-worse air turns up on roughly 99% of them.

0%25%50%75%100%151015202531
Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1217774
2216793
3215803
4115813
5115813
6114823
7114823
8114823
9114823
10114823
11114823
12114823
13214813
14213823
15213823
16213823
17213823
18213823
19213823
20213823
21213823
22113833
23113833
24112843
25112843
26112852
27113842
28113842
29113842
30114832
31114832

Wind in January

Winds average 17 km/h in January.

Across January, daily wind ranges from about 17 km/h on the calmest days to 18 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202531
Wind speed (km/h)Feels
118light breeze
218light breeze
318light breeze
417light breeze
517light breeze
617light breeze
717light breeze
817light breeze
917light breeze
1017light breeze
1117light breeze
1217light breeze
1317light breeze
1417light breeze
1517light breeze
1617light breeze
1717light breeze
1817light breeze
1917light breeze
2017light breeze
2117light breeze
2217light breeze
2317light breeze
2417light breeze
2517light breeze
2617light breeze
2717light breeze
2817light breeze
2917light breeze
3017light breeze
3117light breeze

Sunrise & sunset in January

DaylightNight

Daylight runs from about 11 h 30 min at the start of January to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 6 minutes over January. Sunrise moves from 6:40 AM to 6:46 AM, and sunset from 6:07 PM to 6:21 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
111.56:406:07
211.56:406:07
311.56:416:08
411.56:416:09
511.56:416:09
611.56:426:10
711.56:426:10
811.56:426:11
911.56:436:11
1011.56:436:12
1111.56:436:12
1211.56:446:13
1311.56:446:13
1411.56:446:14
1511.56:446:14
1611.56:456:15
1711.56:456:15
1811.56:456:15
1911.56:456:16
2011.56:456:16
2111.56:456:17
2211.56:466:17
2311.56:466:18
2411.56:466:18
2511.56:466:19
2611.66:466:19
2711.66:466:19
2811.66:466:20
2911.66:466:20
3011.66:466:21
3111.66:466:21

Solar energy in January

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in January, about 5.2 kWh/m².

For context, solar energy here swings from a low near 4.49 kWh/m² to a high of 6.44 kWh/m² in April across the year — January's 5.2 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
14.9Bright
24.9Bright
34.9Bright
44.9Bright
55.0Bright
65.0Bright
75.0Bright
85.0Bright
95.1Bright
105.1Bright
115.1Bright
125.1Bright
135.2Bright
145.2Bright
155.2Bright
165.2Bright
175.3Bright
185.3Bright
195.3Bright
205.3Bright
215.3Bright
225.4Bright
235.4Bright
245.4Bright
255.4Bright
265.5Bright
275.5Bright
285.5Bright
295.5Bright
305.6Bright
315.6Bright
Planning a trip in January

Hazard calendar for Ko Samui

In seasonPeak

None of Ko Samui's seasonal hazards are active in January. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Ko Samui sits in the North Indian Ocean cyclone zone; the season peaks May and October–November.

Ko Samui's rainy season runs September–December, when most of the year's rain falls.

Cyclone
Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is January a good time to visit Ko Samui?

Our two travel scores rate January for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

6.7
Sightseeing
2nd-best month of the year
6.8
Beach & pool
3rd-best month of the year

January is a reasonable time to visit Ko Samui for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Ko Samui in January

From January's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In January, Ko Samui sees daytime highs around 27°C and nights near 26°C. Pack light clothes. Worth having: rain gear and sun protection. About 9 days see rain.

light clothesrain gearsun protection

Sea temperature near Ko Samui in January

The nearest coast averages about 28°C in January — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea offshore is warmest in May at about 30°C and coldest in January near 28°C.

The water stays above 20°C all year — warm enough for a swim any month.

26°28°30°32°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan28Warm
Feb28Tropical
Mar29Tropical
Apr30Tropical
May30Tropical
Jun30Tropical
Jul30Tropical
Aug29Tropical
Sep29Tropical
Oct29Tropical
Nov29Tropical
Dec28Warm

UV index in Ko Samui in January

LowModerateHighVery highExtreme

Clear-sky midday UV in January peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Ko Samui peaks around August 22 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 18 at about 10 (very high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highAug 22UV 14Dec 18UV 10
UV index (midday)Level
Jan10Very high
Feb12Extreme
Mar13Extreme
Apr13Extreme
May13Extreme
Jun12Extreme
Jul11Extreme
Aug14Extreme
Sep13Extreme
Oct11Extreme
Nov10Extreme
Dec10Very high

Air quality in Ko Samui in January

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where January falls, not just the annual average.

Air quality in Ko Samui is worst in January — around 16 µg/m³ PM2.5 (moderate), and holds fairly steady the rest of the year.

Modeled monthly averages (CAMS reanalysis, 2015–2024).

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodJan 2016 µg/m³Nov 1110 µg/m³
PM2.5 (µg/m³)Level
Jan16Moderate
Feb15Moderate
Mar13Moderate
Apr14Moderate
May13Moderate
Jun14Moderate
Jul15Moderate
Aug12Good
Sep12Good
Oct11Good
Nov10Good
Dec12Moderate
Location & terrain

Where is Ko Samui?

Ko Samui sits at 9.5°N, 99.9°E, 8 m above sea level, in Thailand. The nearest listed city is Ko Pha-ngan, 27 km away.

Ban Na SanLang SuanNakhon Si ThammaratPak Phanang

Topography around Ko Samui

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Ko Samui.

Within 3 km, the terrain around Ko Samui has significant variations in elevation — a maximum elevation change of 476 m around an average of 56 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 629 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,358 m.

The land around Ko Samui is covered by trees (51%) and water (42%) within 3 km, water (72%) and trees (24%) within 16 km, and water (82%) within 80 km.

3 km
476 m
16 km
629 m
80 km
1,358 m
treesgrasslandartificial surfaceswater
January weather nearby: Ko Pha-ngan 27 km · Ko Tao 63 km · Surat Thani 79 km · Tha Kham 91 km · Ban Na San 103 km · Lang Suan 104 km · Nakhon Si Thammarat 123 km · Pak Phanang 135 km

Thailand travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type A / B / C
230 V · 50 Hz
Prices
≈ 31% of US
price level, 2025
GDP per capita
$8,057
2025
Happiness
6.3 / 10
World Happiness, 2025
Homicide rate
4.8
per 100k, 2011
Road deaths
32.2
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Very low
EF EPI 402
Religion
Buddhist 93%Muslim 5%Christian 1%other 1%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Ko Samui (9.5357°, 99.9357°, elevation 8 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).