Ko Samui weather in August

In August, Ko Samui sees average daytime highs of 29°C and overnight lows near 27°C, with 91 mm of rain across 18 wet days and about 12.3 hours of daylight. It is the 5th-warmest and 7th-wettest month of the year here.

Day-to-day highs hold fairly steady near 29°C through the month. The sky is clear or mostly clear about 5% of the time in August, and the air most often feels oppressive.

Daylight stretches from about 12 h 24 min at the start of August to 12 h 12 min by month's end. Set against the rest of the year, August is Ko Samui's 10th-clearest and 1st-windiest month. For the whole year in context, see Ko Samui's year-round climate.

Daytime high
29°
5th warmest
Overnight low
27°
7th coldest
Rainfall
91 mm
18 wet days
Daylight
12 h 18 min
6:15 AM – 6:34 PM
Cloud cover
84%
10th clearest
Wind
19 km/h
1st windiest
Solar energy
5.54 kWh/m²
Travel score
4.3
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 August

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 29°C through the month.

A typical August day in Ko Samui reaches about 29°C in the afternoon and slips back to 27°C overnight — a 2°C spread between the day's warmth and the night's chill. On most days the high lands between 28°C and 30°C. Set against its neighbours, August runs on par with July and on par with September.

24°26°28°30°32°151015202531
Avg high (°C)Avg low (°C)
12927
22927
32927
42927
52927
62927
72927
82927
92927
102927
112927
122927
132927
142927
152927
162927
172927
182927
192927
202927
212927
222927
232927
242927
252927
262927
272927
282927
292927
302927
312827

How August really feels in Ko Samui

Once humidity and wind are folded in, August averages 31 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
31
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

The story in August is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

Ko Samui weather by month

How August compares with the rest of the year at a glance. August is the 5th-warmest and 7th-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 August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 5% of the time in August.

Beyond those clear spells, partly cloudy skies cover about 8% of August, with mostly cloudy or overcast conditions the remaining 86%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
11189
21189
31189
41189
51288
61288
71387
81387
91387
101486
111486
121585
131585
141585
151585
161585
171585
181585
191684
201585
211585
221585
231486
241486
251486
261486
271486
281387
291387
301288
311288

Chance of precipitation in August

Any precipitation

Ko Samui gets around 91 mm of rain over 18 wet days in August. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 59% and peaks near 67% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%80%151015202531
Rain chance (%)
158
258
358
457
557
656
756
856
955
1055
1155
1255
1355
1455
1556
1656
1757
1857
1958
2058
2159
2260
2361
2462
2563
2663
2764
2865
2966
3067
3167

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, August lands in the oppressive band about 61% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202531
Oppressive (%)Miserable (%)
15644
25644
35743
45842
55941
65941
76040
86040
96040
106139
116139
126139
136139
146139
156139
166139
176139
186139
196139
206139
216139
226139
236139
246139
256238
266238
276337
286337
296436
306436
316535

Wind in August

Winds average 19 km/h in August, the windiest month of the year.

Across August, daily wind ranges from about 18 km/h on the calmest days to 20 km/h at its breeziest. It stays fairly steady from day to day.

0510152025151015202531
Wind speed (km/h)Feels
120light breeze
220light breeze
320light breeze
420light breeze
520light breeze
620light breeze
720light breeze
819light breeze
919light breeze
1019light breeze
1119light breeze
1219light breeze
1319light breeze
1419light breeze
1519light breeze
1619light breeze
1719light breeze
1819light breeze
1919light breeze
2019light breeze
2119light breeze
2219light breeze
2319light breeze
2418light breeze
2518light breeze
2618light breeze
2718light breeze
2818light breeze
2918light breeze
3018light breeze
3118light breeze

Sunrise & sunset in August

DaylightNight

Daylight runs from about 12 h 24 min at the start of August to 12 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 12 minutes over August. Sunrise moves from 6:14 AM to 6:14 AM, and sunset from 6:39 PM to 6:26 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
112.46:146:39
212.46:146:39
312.46:146:38
412.46:146:38
512.46:146:38
612.46:146:38
712.46:146:37
812.46:146:37
912.46:146:37
1012.46:156:36
1112.46:156:36
1212.36:156:36
1312.36:156:35
1412.36:156:35
1512.36:156:34
1612.36:156:34
1712.36:156:33
1812.36:156:33
1912.36:156:32
2012.36:156:32
2112.36:156:32
2212.36:156:31
2312.36:156:31
2412.36:156:30
2512.26:156:29
2612.26:156:29
2712.26:156:28
2812.26:156:28
2912.26:156:27
3012.26:156:27
3112.26:146:26

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 5.54 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 — August's 5.54 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
15.4Bright
25.4Bright
35.4Bright
45.5Bright
55.5Bright
65.5Bright
75.5Bright
85.5Bright
95.6Bright
105.6Bright
115.6Bright
125.6Bright
135.6Bright
145.6Bright
155.6Bright
165.6Bright
175.6Bright
185.6Bright
195.6Bright
205.6Bright
215.6Bright
225.6Bright
235.6Bright
245.5Bright
255.5Bright
265.5Bright
275.5Bright
285.5Bright
295.5Bright
305.5Bright
315.5Bright
Planning a trip in August

Hazard calendar for Ko Samui

In seasonPeak

None of Ko Samui's seasonal hazards are active in August. 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 August a good time to visit Ko Samui?

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

4.3
Sightseeing
7th-best month of the year
5.3
Beach & pool
7th-best month of the year

August is a reasonable time to visit Ko Samui for sightseeing.

What to pack for Ko Samui in August

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

In August, Ko Samui sees daytime highs around 29°C and nights near 27°C. Pack light clothes and rain gear. Worth having: sun protection. About 18 days see rain.

light clothesrain gearsun protection

Sea temperature near Ko Samui in August

The nearest coast averages about 29°C in August — 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 August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks around 14 (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 August

GoodModeratePoorUnhealthyVery unhealthy

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