Thailand · 30-year monthly climate averages
Based on 30 years of climate data, the most comfortable months to visit Ko Samui are January, February and April, when daytime temperatures are agreeable and rainfall is relatively low.
Ko Samui sees its warmest weather in May, when daytime highs average around 33°C, and its coolest in January (around 29°C).
Annual precipitation totals roughly 1994mm — November is typically the wettest month (~445mm) and February the driest (~64mm).
A distinctly wetter period runs from September to January — worth planning around if you prefer dry days.
🟧 avg daytime high · 🟦 dashed: avg nighttime low · bars: monthly rainfall
Daily forecast highs vs the 30-year normal — last 60 days
Each bar is one day: orange above normal, blue below.
| Month | High / Low | Rainfall | Travel rating |
|---|---|---|---|
| January | 29° / 24°C | 127mm | 👍 Good |
| February | 29° / 25°C | 64mm | 👍 Good |
| March | 30° / 25°C | 116mm | 🤔 Fair |
| April | 32° / 26°C | 83mm | 🤔 Fair |
| May | 33° / 26°C | 132mm | 🤔 Fair |
| June | 33° / 25°C | 134mm | 🤔 Fair |
| July | 32° / 25°C | 117mm | 🤔 Fair |
| August | 32° / 25°C | 102mm | 🤔 Fair |
| September | 32° / 25°C | 118mm | 🤔 Fair |
| October | 31° / 24°C | 295mm | ⚠️ Challenging |
| November | 30° / 24°C | 445mm | 🤔 Fair |
| December | 29° / 24°C | 263mm | 🤔 Fair |
January in Ko Samui is warm, with average daytime highs around 29°C (84°F) and nighttime lows near 24°C (76°F). Expect roughly 127mm of precipitation spread over about 9 rainy days, and this is one of the wetter months.
🎒 What to pack — light summer clothing · sunscreen and sunglasses · compact umbrella or rain jacket
February in Ko Samui is warm, with average daytime highs around 29°C (85°F) and nighttime lows near 25°C (77°F). Expect roughly 64mm of precipitation spread over about 4 rainy days, with a moderate amount of rain.
🎒 What to pack — light summer clothing · sunscreen and sunglasses
March in Ko Samui is hot, with average daytime highs around 30°C (87°F) and nighttime lows near 25°C (78°F). Expect roughly 116mm of precipitation spread over about 5 rainy days, and this is one of the wetter months.
🎒 What to pack — breathable summer clothing · sunscreen, hat and sunglasses · refillable water bottle · compact umbrella or rain jacket
April in Ko Samui is hot, with average daytime highs around 32°C (89°F) and nighttime lows near 26°C (79°F). Expect roughly 83mm of precipitation spread over about 6 rainy days, with a moderate amount of rain.
🎒 What to pack — breathable summer clothing · sunscreen, hat and sunglasses · refillable water bottle
May in Ko Samui is hot, with average daytime highs around 33°C (91°F) and nighttime lows near 26°C (78°F). Expect roughly 132mm of precipitation spread over about 11 rainy days, and this is one of the wetter months.
🎒 What to pack — breathable summer clothing · sunscreen, hat and sunglasses · refillable water bottle · compact umbrella or rain jacket
June in Ko Samui is hot, with average daytime highs around 33°C (91°F) and nighttime lows near 25°C (78°F). Expect roughly 134mm of precipitation spread over about 10 rainy days, and this is one of the wetter months.
🎒 What to pack — breathable summer clothing · sunscreen, hat and sunglasses · refillable water bottle · compact umbrella or rain jacket
July in Ko Samui is hot, with average daytime highs around 32°C (90°F) and nighttime lows near 25°C (77°F). Expect roughly 117mm of precipitation spread over about 11 rainy days, and this is one of the wetter months.
🎒 What to pack — breathable summer clothing · sunscreen, hat and sunglasses · refillable water bottle · compact umbrella or rain jacket
August in Ko Samui is hot, with average daytime highs around 32°C (90°F) and nighttime lows near 25°C (77°F). Expect roughly 102mm of precipitation spread over about 11 rainy days, with a moderate amount of rain.
🎒 What to pack — breathable summer clothing · sunscreen, hat and sunglasses · refillable water bottle
September in Ko Samui is hot, with average daytime highs around 32°C (89°F) and nighttime lows near 25°C (77°F). Expect roughly 118mm of precipitation spread over about 11 rainy days, and this is one of the wetter months.
🎒 What to pack — breathable summer clothing · sunscreen, hat and sunglasses · refillable water bottle · compact umbrella or rain jacket
October in Ko Samui is hot, with average daytime highs around 31°C (87°F) and nighttime lows near 24°C (76°F). Expect roughly 295mm of precipitation spread over about 16 rainy days, and heavy rainfall is common — this is peak wet season territory.
🎒 What to pack — breathable summer clothing · sunscreen, hat and sunglasses · refillable water bottle · compact umbrella or rain jacket
November in Ko Samui is warm, with average daytime highs around 30°C (85°F) and nighttime lows near 24°C (75°F). Expect roughly 445mm of precipitation spread over about 17 rainy days, and heavy rainfall is common — this is peak wet season territory.
🎒 What to pack — light summer clothing · sunscreen and sunglasses · compact umbrella or rain jacket
December in Ko Samui is warm, with average daytime highs around 29°C (85°F) and nighttime lows near 24°C (75°F). Expect roughly 263mm of precipitation spread over about 12 rainy days, and heavy rainfall is common — this is peak wet season territory.
🎒 What to pack — light summer clothing · sunscreen and sunglasses · compact umbrella or rain jacket