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.
Across the year, the best time to visit Ko Samui is January–April.
Based on KO SAMUI, TH (14.7km), 1995–2024. 24 years of January data.