Best months to visit
December
January to April is the classic Samui window — dry, sunny, calm sea. February and March are the most reliable months. May-September has occasional showers but plenty of beach weather. October-December is the rainy season (peak November); accommodation is half-price but expect 20-25 rainy days/month.
Best for
Beach
January-April — Chaweng, Lamai and Bophut are calm, dry and warm (sea 29-31 °C). Full beach service.
Hiking
January-March — Hin Lat and Na Muang waterfalls, and Khao Pom viewpoints, are coolest and driest then.
Sightseeing
January-April — Big Buddha, Wat Plai Laem and Bophut Fisherman's Village all most pleasant in dry-season weather; ferry connections to Koh Phangan reliable.
Climate notes
- Late-year wet season (October-December): the NE monsoon retreats moisture into the Gulf of Thailand, dumping 190-320 mm of rain per month — the OPPOSITE timing to the Andaman side (Phuket, Phi Phi). November is the peak.
- Long dry-warm window (January-April): the Gulf turns calm and bright; Samui's classic 'sunny season' from January through April with rainfall 40-100 mm/month, sea 28-31 °C.
- Mid-year shoulder (May-September): the SW monsoon brings less rain to the Gulf side than to the Andaman side — Samui sees 78-140 mm/month — usable beach weather punctuated by short squalls.
- Sea-temperature peak: Gulf of Thailand sea hits 31 °C in April-May — among the warmest beach water on Earth.
- Tropical thunderstorms: short, intense afternoon downpours in shoulder seasons (May, October); mornings often clear.
- Cyclone-rare: at 9°N Samui sits below the typical typhoon track; tropical storms recurving from the South China Sea (rare) can amplify wet-season rain. Direct typhoon hits historically rare.
Temperature (min / max °C)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Rainy days per month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Sunshine hours per month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Regional notes
- Chaweng (east coast): the busiest beach with widest range of accommodation; sheltered from SW monsoon, exposed to NE monsoon storms in November.
- Lamai (south-east): quieter than Chaweng, similar weather pattern.
- Bophut and Big Buddha (north): sheltered most of the year by Koh Phangan to the north; calm sea even in November storms.
- Lipa Noi and Nathon (west): main ferry pier; calm during NE monsoon, choppier in SW monsoon (May-September) when winds and waves come from the west.
- Khao Pom and inland (200-500 m): cooler and wetter than coast; jungle rainforest with waterfalls.
Frequently asked questions
When is the best time to visit Koh Samui?
January to April — the dry season. February and March have the most reliable sun, calm sea, and comfortable humidity. December-January is busiest with festive crowds; April is hottest before the SW monsoon shoulder begins.
Andaman vs Gulf of Thailand — what is the difference for Koh Samui?
Critical distinction. Samui is on the Gulf side, so wet season is October-December (peak November). Andaman islands (Phuket, Phi Phi, Koh Lanta) have OPPOSITE timing — wet May-October. If you want sun in October-November, choose the Andaman; in December-February, both sides are dry.
Can I visit Koh Samui in November?
Possible but the wettest month. Expect 25 rainy days, with storms that can flood roads. November is when the worst tropical disturbances cross the Gulf. Many travellers shift to October or December if they want the same lower prices with less weather risk.
Is Koh Samui rainy in July-August?
Lighter than the Andaman side. Samui's SW monsoon shoulder brings 100-140 mm/month with mornings often clear and afternoon showers. Many travellers consider July-September a quietly pleasant alternative to peak season.
Does Koh Samui get typhoons?
Direct typhoon hits are historically rare. Tropical depressions recurving from the South China Sea cross the Gulf occasionally, amplifying November rain — Tropical Storm Pabuk (January 2019) was a notable exception. At 9°N Samui sits below the main typhoon belt.
When is the best diving around Koh Samui?
January-May — calm Gulf, visibility 10-20 m, peak season for whale shark sightings near Sail Rock (between Samui and Koh Tao). June-October bring slightly worse visibility but still operational. November is the worst month for dive operations.
What is the temperature in Koh Samui in February?
Daytime 28-32 °C, nights 24-26 °C, sea 28-29 °C. Humidity 70-80 %. Bright, dry, comfortable — peak high season.
Can I ferry from Koh Samui to Koh Tao year-round?
Yes — the catamaran services run all year. Schedules can be reduced or weather-deferred during November storms; one-day disruption is the typical worst case.
Climate data: Open-Meteo · 2020–2025