Ko Samui weather in December

In December, Ko Samui sees average daytime highs of 27°C and overnight lows near 26°C, with 145 mm of rain across 13.2 wet days and about 11.5 hours of daylight. It is the 11th-warmest and 3rd-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 23% of the time in December, and the air most often feels oppressive.

Daylight stretches from about 11 h 30 min at the start of December to 11 h 30 min by month's end. Set against the rest of the year, December is Ko Samui's 5th-clearest and 2nd-windiest month. For the whole year in context, see Ko Samui's year-round climate.

Daytime high
27°
11th warmest
Overnight low
26°
2nd coldest
Rainfall
145 mm
13.2 wet days
Daylight
11 h 24 min
6:33 AM – 6:00 PM
Cloud cover
64%
5th clearest
Wind
18 km/h
2nd windiest
Solar energy
4.64 kWh/m²
Travel score
5.9
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 December

Average highAverage lowShaded bands: 10–90% of days

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

A typical December 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, December runs on par with November and on par with January.

24°26°28°30°32°151015202531
Avg high (°C)Avg low (°C)
12826
22826
32826
42826
52826
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 December really feels in Ko Samui

Once humidity and wind are folded in, December 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

December 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 December compares with the rest of the year at a glance. December is the 11th-warmest and 3rd-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 December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 23% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 19% of December, with mostly cloudy or overcast conditions the remaining 57%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13862
23862
33862
43961
53961
63862
73961
83961
93961
104060
114060
124060
134159
144159
154159
164258
174357
184357
194456
204456
214555
224654
234753
244753
254852
264852
274852
284951
294951
304951
314951

Chance of precipitation in December

Any precipitation

Ko Samui gets around 145 mm of rain over 13.2 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 43% and peaks near 57% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%151015202531
Rain chance (%)
157
256
355
454
553
652
751
850
949
1048
1148
1247
1346
1445
1544
1643
1741
1840
1939
2038
2137
2237
2336
2435
2535
2634
2734
2834
2934
3034
3134

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, December lands in the oppressive band about 75% of days. Sticky, muggy-or-worse air turns up on roughly 99% of them.

0%25%50%75%100%151015202531
Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1077122
2077122
3087121
4087220
5097219
6097318
7097417
80107515
90107614
100107713
110117712
120117811
130127711
140127810
15013789
16013789
17114778
18115768
19115777
20116767
21116767
22117757
23117766
24218746
25218746
26219745
27219745
28219745
29218764
30218764
31217774

Wind in December

Winds average 18 km/h in December.

Across December, daily wind ranges from about 18 km/h on the calmest days to 19 km/h at its breeziest. It stays fairly steady from day to day.

0510152025151015202531
Wind speed (km/h)Feels
118light breeze
218light breeze
318light breeze
418light breeze
518light breeze
618light breeze
718light breeze
818light breeze
918light breeze
1018light breeze
1118light breeze
1218light breeze
1318light breeze
1418light breeze
1518light breeze
1619light breeze
1719light breeze
1819light breeze
1919light breeze
2019light breeze
2119light breeze
2218light breeze
2318light breeze
2418light breeze
2518light breeze
2618light breeze
2718light breeze
2818light breeze
2918light breeze
3018light breeze
3118light breeze

Sunrise & sunset in December

DaylightNight

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

Days grow by about 0 minutes over December. Sunrise moves from 6:26 AM to 6:40 AM, and sunset from 5:55 PM to 6:07 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
111.56:265:55
211.56:265:55
311.56:275:55
411.56:275:55
511.56:275:56
611.56:285:56
711.56:295:56
811.56:295:57
911.56:305:57
1011.56:305:57
1111.56:315:58
1211.56:315:58
1311.56:325:59
1411.46:325:59
1511.46:335:59
1611.46:336:00
1711.46:346:00
1811.46:346:01
1911.46:346:01
2011.46:356:02
2111.46:356:02
2211.46:366:03
2311.46:366:03
2411.46:376:03
2511.46:376:04
2611.46:386:04
2711.46:386:05
2811.46:396:05
2911.46:396:06
3011.46:396:06
3111.56:406:07

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 4.64 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 — December's 4.64 kWh/m² sits near the bottom.

024151015202531
Solar energy (kWh/m²)Level
14.5Bright
24.5Bright
34.5Bright
44.5Bright
54.5Bright
64.5Bright
74.5Bright
84.5Bright
94.5Bright
104.5Bright
114.6Bright
124.6Bright
134.6Bright
144.6Bright
154.6Bright
164.7Bright
174.7Bright
184.7Bright
194.7Bright
204.7Bright
214.8Bright
224.8Bright
234.8Bright
244.8Bright
254.8Bright
264.8Bright
274.8Bright
284.8Bright
294.9Bright
304.9Bright
314.9Bright
Planning a trip in December

Hazard calendar for Ko Samui

In seasonPeak

In December, Ko Samui sits inside its cyclone and rainy season season. The full year is below, with each hazard's peak months called out.

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 December a good time to visit Ko Samui?

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

5.9
Sightseeing
4th-best month of the year
6.1
Beach & pool
5th-best month of the year

December 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 December

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

In December, Ko Samui sees daytime highs around 27°C and nights near 26°C. Pack light clothes. Worth having: rain gear and sun protection. About 13 days see rain.

light clothesrain gearsun protection

Sea temperature near Ko Samui in December

The nearest coast averages about 28°C in December — 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 December

LowModerateHighVery highExtreme

Clear-sky midday UV in December 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 December

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where December 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
December 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).