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Contents
- The climate of Ko Samui
- The best time to visit Ko Samui
- The worst time to visit Ko Samui
- Spring weather in Ko Samui
- Summer weather in Ko Samui
- Autumn weather in Ko Samui
- Winter weather in Ko Samui
- Weather in January
- Weather in February
- Weather in March
- Weather in April
- Weather in May
- Weather in June
- Weather in July
- Weather in August
- Weather in September
- Weather in October
- Weather in November
- Weather in December
- Frequently asked questions
- Average temperature
- Average humidity
- Average rainfall
- Average rainfall days
- Average sea temperature
- Average daylight
- Average sunshine
- Average UV index
The striking Angthong National Marine Park in Ko Samui, Thailand
The climate of Ko Samui
Ko Samui, a tropical haven located in the Gulf of Thailand, is classified under the Köppen climate system as a tropical rainforest climate. This type of climate is characterized by high temperatures and abundant rainfall throughout the year. This island experiences a hardly noticeable annual temperature variation, with an average high temperature ranging from 29°C (84.2°F) in January and November to 32.6°C (90.7°F) in April. The average low temperature varies between 24.1°C (75.4°F) in November and 26.1°C (79°F) in April.
Relative humidity remains high throughout the year, averaging from 78% in July, August, and September, to a noticeable peak of 85% in October and November. Sea temperatures remain fairly constant from 27.8°C (82°F) in January to a slightly warmer 30.1°C (86.2°F) in May. These warm temperatures make Ko Samui a perfect beach destination at any time of the year. Daylight hours show a slight increase from 11.6 in January and December to a peak of 12.7 in June.
Regarding rainfall, there is a significant difference throughout the year. Drier months like February offer about 54mm (2.13") of rainfall, whereas November shows a stark contrast with a heavy downpour of approximately 507mm (19.96"). Correspondingly, the number of rainy days ranges from 4 to 5 days in February and March to a high of 20 days in October and November.
Relative humidity remains high throughout the year, averaging from 78% in July, August, and September, to a noticeable peak of 85% in October and November. Sea temperatures remain fairly constant from 27.8°C (82°F) in January to a slightly warmer 30.1°C (86.2°F) in May. These warm temperatures make Ko Samui a perfect beach destination at any time of the year. Daylight hours show a slight increase from 11.6 in January and December to a peak of 12.7 in June.
Regarding rainfall, there is a significant difference throughout the year. Drier months like February offer about 54mm (2.13") of rainfall, whereas November shows a stark contrast with a heavy downpour of approximately 507mm (19.96"). Correspondingly, the number of rainy days ranges from 4 to 5 days in February and March to a high of 20 days in October and November.
The best time to visit Ko Samui
Given the climate characteristics of Ko Samui, the best time to visit would be during the drier months of February and March. During this period, visitors can expect less rainfall, approximately 54mm (2.13") and 81mm (3.19") respectively, and fewer rainy days. The number of sunshine hours sits at a higher-scale of 8-9 hours per day, and the UV index reaches its top level at 12. This makes for excellent weather conditions for sunbathing and exploring the natural beauty of the island.
The worst time to visit Ko Samui
Conversely, the worst time to make a visit to Ko Samui would be in November due to the highest rainfall amount of 507mm (19.96") and the considerable number of rainy days reaching up to 20. Despite the warm sea temperature of 29.2°C (84.6°F), the high relative humidity of 85% combined with substantial rain might make outdoor activities and exploration less enjoyable.
Spring weather in Ko Samui
Spring in Ko Samui, constitutes of the months from March to May, and exhibits increasing temperatures. Average high temperatures climb from 30.6°C (87.1°F) to 32.6°C (90.7°F), while the average low hovers between 25.6°C (78.1°F) and 25.7°C (78.3°F). March records less rainfall of 81mm (3.19"), whilst May sees a significant increase up to 156mm (6.14"). The sea warms up gradually from 28.8°C (83.8°F) to 30.1°C (86.2°F), and daylight extends from 12.1 hours to 12.6 hours.
Summer weather in Ko Samui
The summer months of June, July, and August, illustrate relatively stable temperatures, with the average highs oscillating between 32.5°C (90.5°F) and 32.1°C (89.8°F) and average lows from 25.7°C (78.3°F) to 25.2°C (77.4°F). The monthly rainfall ranges from 124mm (4.88") in June to 111mm (4.37") in August. Sea temperature remains steady at 29.8°C (85.6°F), with a slight reduction in the hours of daylight from 12.7 in June to 12.4 in August.
Autumn weather in Ko Samui
In autumn, encompassing September to November, temperatures slightly decrease, averaging from 30.5°C (86.9°F) to 29.2°C (84.6°F) for highs and 24.8°C (76.6°F) to 24.1°C (75.4°F) for lows. Rainfall soars, especially in November when it reaches a whopping 507mm (19.96"). Correspondingly, the number of rainy days increases to 20 in October and November. Despite this, the sea temperature remains quite stable at around 29.2°C (84.6°F) to 29.3°C (84.7°F).
Winter weather in Ko Samui
Winter in Ko Samui is from December to February and is generally warmer with average high temperatures ranging from 32°C (89.6°F) in December to 29.4°C (84.9°F) in February. The lowest temperature averages around 24°C (75.2°F) throughout this period. Rainfall decreases dramatically during winter, with December recording 210mm (8.27") descending to 54mm (2.13") in February. Simultaneously, the sea temperature drops slightly to 28.2°C (82.8°F) in December, though it measures up to 28.1°C (82.6°F) by February.
Weather in January
January receives 86mm (3.39") of rain, making it one of the driest months in the year for Ko Samui, Thailand. With these weather conditions, tourists find this month perfect for their travel plans. The cool sea breeze adds a layer of comfort to the prevailing weather. Weather in January »
Weather in February
February in Ko Samui, Thailand, marks a transition between the drier months and the upcoming wetter period. Relative to January, it is a bit drier with 54mm (2.13") of rain. Visitors can enjoy the beach under sunshine for a longer duration, a trait that carries over to the following month. Weather in February »
Weather in March
In Ko Samui, Thailand, the arrival of March brings a significant shift in the weather. Although similar to February, more rainfall can be observed with an accumulation of 81mm (3.19") over the month. Although there's an increase in rainfall, the quantity of sunny days remains fairly constant. Weather in March »
Weather in April
Weather in Ko Samui, Thailand, during April is characterized by a drastic increase in rainfall from 81mm (3.19") to 83mm (3.27") compared to March. This is a month where the region transitions into monsoon season. Despite the mounting rainfall, the number of sunny days remains unaffected, keeping the beach a popular attraction. Weather in April »
Weather in May
Ko Samui, Thailand, sees May as a month featuring the year's first significant jump in rainfall to 156mm (6.14"). The pre-monsoon showers lead to a more comfortable and enjoyable climate in the region. The sea remains warm and inviting despite the uptick in rainfall. Weather in May »
Weather in June
June's weather in Ko Samui, Thailand, fluctuates noticeably from May. A decrease in rain from 156mm (6.14") to 124mm (4.88") means that showers are still frequent but not as heavy. The temperature peaks to its highest, which blends with unique summer rainfall. Weather in June »
Weather in July
July in Ko Samui, Thailand, remains reasonably stable with no drastic changes. The rainfall stays relatively constant around 116mm (4.57"), slightly less than June. Despite the monsoon, an equal amount of sunny and rainy days persists. Weather in July »
Weather in August
August in Ko Samui, Thailand, mirrors the weather patterns of July. With the drop in rainfall to 111mm (4.37"), it is one of the more moderate months during monsoon. The sea temperature begins to drop, yet it remains comfortable for beachgoers. Weather in August »
Weather in September
The weather in Ko Samui, Thailand, in September can be characterized by a slight rise in rainfall to 122mm (4.8") relative to August. This month acts as a link between the rainy season and the impending drier period. Beaches retain their charm with sea temperature and daylight hours holding steady. Weather in September »
Weather in October
October in Ko Samui, Thailand, stands out as the month with the most rainfall at 310mm (12.2"). This massive increase in rainfall signifies the height of the monsoon season. Despite the heavy showers, the city's beauty remains undiluted. Weather in October »
Weather in November
Ko Samui, Thailand, in November experiences the year's highest amount of rainfall measuring 507mm (19.96"). This exceptional volume of rain signifies the peak of the monsoon season. The main highlights are the lush greenery and fresh atmosphere that these showers bring along. Weather in November »
Weather in December
December in Ko Samui, Thailand, explains a significant decrease in rainfall to 210mm (8.27") from November. The dense monsoon clouds start to clear up spelling out a shift towards drier months. Temperatures remain steady, promising comfortable holiday weather. Weather in December »
[Resources]Frequently asked questions
What is the coldest month in Ko Samui?
In Ko Samui, January registers the lowest temperatures, averaging 29°C (84.2°F) at the peak and 24.2°C (75.6°F) at the lowest.
How many days does it rain in Ko Samui?
In Ko Samui, Thailand, during the entire year, the rain falls for 160 days and collects up to 1960mm (77.17") of precipitation.
What month is the sea coldest in Ko Samui?
With an average sea temperature of 27.8°C (82°F), January is the month with the coldest seawater in Ko Samui, Thailand.
What is the driest month in Ko Samui?
February is the month with the least rainfall in Ko Samui. Rain falls for 5 days and accumulates 54mm (2.13") of precipitation.
What month has the most sunshine in Ko Samui?
The month with the most sunshine in Ko Samui is February, with an average of 9h of sunshine.
When is the highest UV index in Ko Samui?
February through October, with an average maximum UV index of 12, are months with the highest UV index.
What are the warmest months in Ko Samui?
The month of April sees the average highest temperatures in Ko Samui, Thailand, reaching 32.6°C (90.7°F) at the peak and 26.1°C (79°F) at the low.
When is the sea warmest in Ko Samui?
With an average sea temperature of 30.1°C (86.2°F), May is the month with the warmest seawater.
What is the month with the least sunshine in Ko Samui?
The months with the least sunshine in Ko Samui are May through December, with an average of 6h of sunshine.
What are the least humid months in Ko Samui?
The months with the lowest humidity in Ko Samui, Thailand, are June through August, with an average relative humidity of 78%.
When are the longest days in Ko Samui?
June has the longest days of the year in Ko Samui, with an average of 12h and 42min of daylight.
What is the most humid month in Ko Samui?
The months with the highest humidity in Ko Samui are October and November, with an average relative humidity of 85%.
What is the rainiest month in Ko Samui?
November is the month with the most rainfall in Ko Samui, Thailand. Rain falls for 20 days and accumulates 507mm (19.96") of precipitation.
What is the month with the shortest days in Ko Samui?
The month with the shortest days in Ko Samui is December, with an average of 11h and 36min of daylight.
Is there Daylight Saving Time (DST) in Ko Samui?
Ko Samui does not utilize Daylight Saving Time (DST). +07 timezone is used over the entire year.
What is the month with the lowest UV index in Ko Samui?
With an average maximum UV index of 10, December is the month with the lowest UV index in Ko Samui.
Average temperature
Ko Samui, Thailand
The warmest month (with the highest average high temperature) is April (32.6°C).
The month with the lowest average high temperature is January (29°C).
The month with the highest average low temperature is April (26.1°C).
The coldest month (with the lowest average low temperature) is December (23.9°C).
Average humidity
Ko Samui, Thailand
The months with the highest relative humidity are October and November (85%).
The months with the lowest relative humidity are June, July and August (78%).
Average rainfall
Ko Samui, Thailand
- Average rainfall in January:
86.2mm - Average rainfall in February:
54.4mm - Average rainfall in March:
80.8mm - Average rainfall in April:
83.1mm - Average rainfall in May:
155.9mm - Average rainfall in June:
124.1mm
- Average rainfall in July:
116.3mm - Average rainfall in August:
110.9mm - Average rainfall in September:
121.7mm - Average rainfall in October:
309.8mm - Average rainfall in November:
506.6mm - Average rainfall in December:
210.3mm
The wettest month (with the highest rainfall) is November (506.6mm).
The driest month (with the least rainfall) is February (54.4mm).
Average rainfall days
Ko Samui, Thailand
- Average rainfall days in January:
11 days - Average rainfall days in February:
5 days - Average rainfall days in March:
4 days - Average rainfall days in April:
8 days - Average rainfall days in May:
16 days - Average rainfall days in June:
15 days
- Average rainfall days in July:
15 days - Average rainfall days in August:
15 days - Average rainfall days in September:
16 days - Average rainfall days in October:
20 days - Average rainfall days in November:
20 days - Average rainfall days in December:
15 days
The months with the highest number of rainy days are October and November (20 days).
The month with the least rainy days is March (4 days).
Average sea temperature
Ko Samui, Thailand
The best month for swimming (with the highest average sea temperature) is May (30.1°C).
The coldest month (with the lowest average sea temperature) is January (27.8°C).
Average daylight / Average sunshine
Ko Samui, Thailand
- Average daylight in January:
11h and 4min - Average daylight in February:
11h and 5min - Average daylight in March:
12h and 1min - Average daylight in April:
12h and 2min - Average daylight in May:
12h and 4min - Average daylight in June:
12h and 4min
- Average daylight in July:
12h and 4min - Average daylight in August:
12h and 2min - Average daylight in September:
12h and 1min - Average daylight in October:
11h and 5min - Average daylight in November:
11h and 4min - Average daylight in December:
11h and 4min
The month with the longest days is June (Average daylight: 12h and 42min).
The month with the shortest days is December (Average daylight: 11h and 36min).
The month with the most sunshine is February (Average sunshine: 9h).
The months with the least sunshine are May, June, July, August, September, October, November and December (Average sunshine: 6h).
Average UV index
Ko Samui, Thailand
The months with the highest UV index are February, March, April, May, June, July, August, September and October (UV index 12).
The month with the lowest UV index is December (UV index 10).
Ko Samui, Thailand
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