| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 29.1° | 24° | 78.1mm | 10.1 | 71 |
| February | 29.5° | 24.8° | 48.5mm | 6.3 | 77 |
| March | 30.5° | 25.2° | 43.9mm | 4.3 | 77 |
| April | 31.9° | 25.9° | 30.1mm | 4.4 | 72 |
| May | 32.9° | 25.6° | 122.4mm | 13.4 | 50 |
| June | 32.9° | 25.4° | 150.3mm | 13.6 | 49 |
| July | 32.4° | 25.3° | 144mm | 16.6 | 48 |
| August | 32.5° | 25.1° | 159.3mm | 14.8 | 48 |
| September | 32° | 24.9° | 137.8mm | 16.8 | 50 |
| October | 30.9° | 24.5° | 307mm | 20.8 | 54 |
| November | 29.8° | 24.1° | 533.8mm | 22 | 59 |
| December | 29.4° | 24° | 308.9mm | 16.1 | 60 |
January in Ko Samui averages a daily high of 29.1°C with nights around 24°C. Expect roughly 10.1 wet days totalling 78.1mm. Generally workable, with some weather to plan around.
February in Ko Samui averages a daily high of 29.5°C with nights around 24.8°C. Expect roughly 6.3 wet days totalling 48.5mm. Comfortable conditions for being outdoors all day.
March in Ko Samui averages a daily high of 30.5°C with nights around 25.2°C. Expect roughly 4.3 wet days totalling 43.9mm. Comfortable conditions for being outdoors all day.
April in Ko Samui averages a daily high of 31.9°C with nights around 25.9°C. Expect roughly 4.4 wet days totalling 30.1mm. Generally workable, with some weather to plan around.
May in Ko Samui averages a daily high of 32.9°C with nights around 25.6°C. Expect roughly 13.4 wet days totalling 122.4mm. Demanding conditions — pack for it and plan indoor options.
June in Ko Samui averages a daily high of 32.9°C with nights around 25.4°C. Expect roughly 13.6 wet days totalling 150.3mm. Demanding conditions — pack for it and plan indoor options.
July in Ko Samui averages a daily high of 32.4°C with nights around 25.3°C. Expect roughly 16.6 wet days totalling 144mm. Demanding conditions — pack for it and plan indoor options.
August in Ko Samui averages a daily high of 32.5°C with nights around 25.1°C. Expect roughly 14.8 wet days totalling 159.3mm. Demanding conditions — pack for it and plan indoor options.
September in Ko Samui averages a daily high of 32°C with nights around 24.9°C. Expect roughly 16.8 wet days totalling 137.8mm. Demanding conditions — pack for it and plan indoor options.
October in Ko Samui averages a daily high of 30.9°C with nights around 24.5°C. Expect roughly 20.8 wet days totalling 307mm. Demanding conditions — pack for it and plan indoor options.
November in Ko Samui averages a daily high of 29.8°C with nights around 24.1°C. Expect roughly 22 wet days totalling 533.8mm. Generally workable, with some weather to plan around.
December in Ko Samui averages a daily high of 29.4°C with nights around 24°C. Expect roughly 16.1 wet days totalling 308.9mm. Generally workable, with some weather to plan around.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Ko Samui peaks at 77.
Based on 30 years of records, January–April scores highest for comfort in Ko Samui, balancing daytime temperature against rainfall.
May is the warmest, averaging a daily high of 32.9°C.
November is the wettest, averaging 533.8mm of rain across roughly 22 wet days.
January is the coolest month, with average daily highs around 29.1°C.