For the most part, Koh Samui weather is hot and sunny – just what you want for a perfect beach holiday. There are two stark exceptions, as well as shoulder seasons, freak acts from the weather gods and, often, a delightfully cooling afternoon downpour. (Hey, it’s the tropics!) Here are our best answers to the question: “I’m coming to Koh Samui in [month]. What will the weather be like?”
Exceptional weather on Koh Samui
First up, two stark exceptions to the “hot and sunny rule”
#1. Rainy season: Koh Samui’s rainy season (typically late October to mid December. Average November rainfall is 1.6 feet of rain). When it rains, it pours.
#2. When it’s really hot and sunny: That would be Koh Samui in April (with Songkran – the water festival – right in the middle). Learn what to wear in Thailand to stay cool (and un-burnt).
Koh Samui weather, month by month
We both caution and cover our rears with this caveat: there’s no guarantee and this is a crazy world.
January: One of the cooler months of the year, with lows dipping to a ‘frigid’ 24.1C (75F). Coming from the tail-end of rainy season, the temperature heats up through the month. If you don’t like strong heat, a New Year trip to Koh Samui would suit you well.
February: Hey guess what, it’s hot and sunny. An average 1 degree Celsius hotter than January, with the lightest rainfall of any month.
March: Hot and getting hotter. By averages, March also has the fewest number of rainy days and, correspondingly, the least median cloud cover.
April: REALLY HOT. April’s a scorcher.
May: For that matter, May’s pretty hot too (with more rainfall than March or April. When it’s this hot, it’s a great way to cut the humidity and cool down).
June/July/August: Popular months on Koh Samui and for good reason. The differences in temperature and average number of rainy days between these three months are hair-splitting. Whether enjoying a northern hemisphere summer holiday, or escaping southern hemisphere winter, it’s a great time of year to visit Koh Samui.
September: Just as nice as August but likely a lot quieter on the island.
October: Starts out gorgeous (nicely hot and sunny). Is, on average, the cloudiest month. Towards the end of October, rainy season might arrive.
November: Typically rainy season. Though it’s as soggy as a sponge, we think November on Koh Samui has a lot to recommend it.
December: The tail-end of rainy season, not-quite-as-hot, but hopefully sunny. Just about perfect for a Santa hat and a Koh Samui Christmas.
Call us biased, but with fresh Samui coconuts on offer every day of the year… can there really be a bad time to come? Use The Koh Samui Guide to answer all your ‘what ifs’, ‘how tos’ and ‘where shoulds’, then start planning the many ways you’ll enjoy the sun and rain of any season.