Koh Samui Weather
Gulf of Thailand · Live forecast, monthly climate & best time to visit
25°C
Overcast · Koh Samui, right now
Is it raining right now in Koh Samui?
No — Koh Samui is dry right now (overcast, 25°C).
Mon
30°25°
💧 51%
Tue
30°23°
💧 55%
Wed
29°23°
💧 86%
Thu
29°23°
💧 74%
Fri
29°23°
💧 65%
Sat
26°24°
💧 76%
Sun
28°24°
💧 65%
Best time to visit Koh Samui
Thailand doesn't have a single rainy season — it has two, running in opposite directions. The Andaman coast (Phuket, Krabi) faces the Indian Ocean and takes the brunt of the southwest monsoon from roughly May to October. The Gulf of Thailand coast around Koh Samui faces the other way and instead gets its wettest weather from the northeast monsoon around October to December — often staying drier during the mainland's rainy season. Bangkok and the upper Gulf (Pattaya, Hua Hin) follow the same broad May–October pattern as the Andaman coast, while Chiang Mai and the north add a hot, hazy “burning season” from around February to April.
For Koh Samui specifically: Feb–Aug sees the fewest rain days of the year, while Sep–Jan is the wettest stretch. Rain rarely lasts all day — see the FAQs below for what to expect.
Koh Samui monthly climate
| Month | Avg. high | Rainy days | What to expect |
|---|---|---|---|
| January | 28°C | 12 days | Tail end of the wet season; showers still possible but skies are clearing. |
| February | 29°C | 6 days | One of the driest, most reliable months to visit. |
| March | 30°C | 5 days | Hot, dry and sunny — a top month for beaches and diving. |
| April | 31°C | 6 days | Hot with the odd short storm; Songkran adds festivities. |
| May | 31°C | 10 days | A brief shower season begins but rarely disrupts a full day outdoors. |
| June | 31°C | 8 days | A quiet dry pocket between the two monsoon seasons. |
| July | 30°C | 9 days | Generally dry with pleasant sea breezes. |
| August | 30°C | 10 days | A mild uptick in rain but still a solid beach month. |
| September | 30°C | 12 days | Rain builds as the northeast monsoon starts to approach. |
| October | 29°C | 17 days | Wet season begins in earnest — unlike the rest of Thailand, Samui's rains peak now. |
| November | 28°C | 18 days | The wettest month of the year; heavy rain and rough seas are common. |
| December | 27°C | 17 days | Still wet early in the month, gradually clearing by the end. |
Typical climate normals compiled from long-term regional patterns — a guide to what to expect, not a live forecast.
Packing & season tips
- Pack for Koh Samui: Beachwear and sun protection for most of the year, but pack a proper rain jacket — not just an umbrella — if visiting October–December.
- Sun protection: Thailand's tropical latitude means strong UV year-round, even on cloudy or rainy days.
- Book ahead in peak season: the driest months are also the busiest and most expensive for flights and hotels.
- Rainy season isn't a reason to skip a trip: expect lower prices, fewer crowds and lush scenery — just plan indoor backup options for late afternoons.
Frequently asked questions
When is the best time to visit Koh Samui?
Feb–Aug tends to be the best window — rainfall is well below the yearly average and days are more reliably sunny. Avoid Sep–Jan if you'd rather not plan around rain.
Does it rain all day during the rainy season in Koh Samui?
Usually not. Thailand's monsoon rain typically falls as short, heavy afternoon or evening downpours that clear within an hour or two, rather than all-day drizzle — mornings are often dry even in the wettest months.
Is Koh Samui hot all year round?
Yes — average daytime highs run from about 27°C in the coolest month to 31°C in the hottest, so it's warm to hot year-round by most visitors' standards. Humidity, not just temperature, is what changes most through the year.
What should I pack for Koh Samui?
Beachwear and sun protection for most of the year, but pack a proper rain jacket — not just an umbrella — if visiting October–December.
Why is Koh Samui's rainy season different from the rest of Thailand?
Koh Samui sits on the Gulf of Thailand side of the peninsula, which faces the northeast monsoon rather than the southwest monsoon that soaks the Andaman coast and mainland from May to October. That flips Samui's wettest months to roughly October–December, while it often stays drier during the mainland's rainy season.