Ko Samui weather by month & the best time to visit
Thailand · beach resort · tropical monsoon climate
The best time to visit Ko Samui is February — its sunniest month (Sunshine Score 86/100), with April close behind. Ko Samui averages about 2,342 hours of sunshine a year. Daytime highs around 28°C / 82°F and roughly 38 mm of rain in February.
When is the best time to visit Ko Samui?
For sunshine, the best time to visit Ko Samui is February, then April. The dullest month is May (65/100, 170 mm of rain). The full month-by-month picture is in the table below.
How sunny is Ko Samui?
Ko Samui gets a moderate 2,342 hours of sunshine a year. February (86/100) is noticeably better than May (65). It ranks #12 of 24 destinations in Thailand for annual sunshine, above the national median of 2,329 hours. Rain has a clear season: the wettest stretch, around November, carries about 42% of the annual 2,088 mm.
Sunshine Score by month
| Month | Score | Day high | Night low | Rain | UV | Sea |
|---|---|---|---|---|---|---|
| January | 68 | 28° / 82°F | 26° / 79°F | 135 mm | 9 | 29° / 84°F |
| February | 86 | 28° / 82°F | 26° / 79°F | 38 mm | 11 | 30° / 86°F |
| March | 72 | 29° / 84°F | 27° / 81°F | 114 mm | 11 | 30° / 86°F |
| April | 76 | 30° / 86°F | 28° / 82°F | 90 mm | 11 | 32° / 90°F |
| May | 65 | 30° / 86°F | 29° / 84°F | 170 mm | 10 | 33° / 91°F |
| June | 65 | 30° / 86°F | 28° / 82°F | 167 mm | 10 | 31° / 88°F |
| July | 65 | 29° / 84°F | 28° / 82°F | 166 mm | 10 | 31° / 88°F |
| August | 66 | 29° / 84°F | 27° / 81°F | 144 mm | 10 | 31° / 88°F |
| September | 65 | 29° / 84°F | 27° / 81°F | 181 mm | 10 | 30° / 86°F |
| October | 65 | 28° / 82°F | 27° / 81°F | 246 mm | 9 | 31° / 88°F |
| November | 65 | 28° / 82°F | 27° / 81°F | 375 mm | 8 | 30° / 86°F |
| December | 65 | 28° / 82°F | 27° / 81°F | 262 mm | 8 | 29° / 84°F |
Sea temperature in Ko Samui by month
The sea off Ko Samui is warmest in May at around 33°C / 91°F, and coolest in January at 29°C / 84°F. The water sits at a comfortable 21°C or warmer roughly all year round. Month-by-month sea-surface temperatures are in the Sea column of the table above.
Nearest destinations
Head-to-head
How Ko Samui compares month by month: Ko Samui vs Nakhon Si Thammarat · Ko Samui vs Surat Thani · Ko Samui vs Rayong · Ko Samui vs Krabi · all comparisons
Ko Samui: questions and answers
What kind of destination is Ko Samui?
Ko Samui is a beach resort in Thailand with a tropical monsoon climate — the sea reaches 33°C at its warmest and is swimmable (21°C+) year-round.
How many hours of sunshine does Ko Samui get a year?
Ko Samui gets about 2,342 hours of sunshine a year, at its best around February.
When is the best time to visit Ko Samui?
The sunniest time to visit Ko Samui is February, when the Sunshine Score peaks at 86/100 (with April close behind). Expect daytime highs around 28°C / 82°F.
What is the least sunny month in Ko Samui?
May is the least sunny month in Ko Samui, scoring 65/100 with about 170 mm of rain.
What is the sea temperature in Ko Samui?
The sea in Ko Samui ranges from about 29°C (January) to 33°C (May). Month-by-month sea temperatures are on this page.
How strong is the sun in Ko Samui?
The typical midday UV index in Ko Samui peaks around 11 (extreme) in February, easing to about 8 (very high) in November. Month-by-month midday UV values are in the UV column of the table on this page.
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