Koh Samui Weather by Month

What to Expect When You Visit

Planning a trip to Koh Samui and wondering which month will give you the best beach days, the sunniest skies, or the fewest soggy flip-flops?

The truth is that while Koh Samui is hot year-round -- with the average daytime high never falling below 25 or exceeding 32°C in any given month, the weather you can expect during your stay will vary depending on the time of year. And for most of the year you'll be exposed to both scorching sun and soaking downpours in varying proportions.

So, here’s your friendly, no-nonsense month-by-month guide to the island’s ever-interesting tropical weather.

January – Cool(ish), Calm & A Great New Year Escape

If you're not a fan of baking under the Thai sun, January is your sweet spot. Early in the month, Samui enjoys its “coolest” weather—around 25°C (77°F), with the coldest nights dipping to a brisk 24°C (75°F). Don’t worry, you’ll still happily wear shorts.By the end of January, temps slip into the low 30s (high 80s°F), perfect for beach days.

February – Sunshine Superstar

February is one of Samui’s best months: warm but not melty, sunny but not scorching. It’s also the driest month of the year. Bring sunglasses. You’ll need them.

March – Sun Worshippers, Assemble

If you're all about waking up to blue skies every day, March is your month. Temperatures start to climb toward April, but the sunshine is glorious.

April – Bring the Heat!

April is the island’s hottest month—expect the kind of heat that makes air-conditioning your best friend. It’s peak “cold drink + shady palm tree” weather.

May – Hot, Bright & Occasionally Stormy (in a Good Way)

May still feels like the hot, dry season, with tons of sunshine—about seven hours a day. Temps hit 28–35°C (82–95°F), but the occasional dramatic tropical shower sweeps in to cool things down. Rain in May feels like nature turning the thermostat down a notch.

June – Sunshine with a Side of Breezy Showers

June still brings loads of sun, but the heat begins to soften. Expect warm days (25–32°C / 77–92°F) and short tropical sprinkles. Come before school holidays and enjoy a quieter island.

July – Hot, Sunny & Not Really Rainy Season

Don’t believe everything you read—July is not Samui’s rainy season. Most days are sunny and hot, with the odd quick tropical storm. An especially wet July means maybe an inch of rain, compared to November’s twelve.

August – Beach Days with a Chance of Mini-Storms

Pretty much a repeat of July: lots of sunshine, the occasional brief storm, and a high around 32°C (90°F). Great beach weather all around.

September – Quieter Beaches, Same Gorgeous Weather

Early September feels just like August—but with fewer people as families head home for the school year. Mid to late September starts to get a little cloudier as the island drifts toward rainy season.

October – Cloudier Skies & Rainy Season on the Horizon

October begins warm and sunny but gradually gets cloudier. It’s one of Samui’s less-sunny months, but still warm and tropical.

November – The Big Splash

November is typically Samui’s wettest month. Think steady tropical rain, choppy seas, and lush, green everything.But if you’re dreaming of naps, books, massages, and rainy-day café hopping—November is a vibe.

December – Rainy Season Winds Down

By mid-December, the island begins to dry out again. It’s warm (26–29°C / 78–84°F), breezy, and often sunny—making Christmas on the beach feel like a brilliant life decision.

Photo: Silver Beach, Koh Samui. Credit: Unsplash+