The sea temperature at Koh Samui today is 30.6 °C (87 °F) – water as warm as a bath. The usual October average is 29.5 °C. Over the last 30 days the sea has warmed from 29.8 °C to 30.6 °C. Swimmable all year – the sea averages 27 °C or more in every month. Source: Sea Temp Map (seatempmap.com) – NASA MUR satellite data and the Copernicus Marine sea forecast.
| Month | Min | Avg | Max |
|---|---|---|---|
| January | 27.4°C / 81.4°F | 27.9°C / 82.2°F | 28.6°C / 83.5°F |
| February | 28.1°C / 82.6°F | 28.5°C / 83.2°F | 28.9°C / 84.0°F |
| March | 28.7°C / 83.6°F | 29.2°C / 84.5°F | 29.7°C / 85.4°F |
| April | 30.2°C / 86.3°F | 30.4°C / 86.8°F | 31.0°C / 87.8°F |
| May | 30.3°C / 86.6°F | 30.8°C / 87.4°F | 31.4°C / 88.6°F |
| June | 30.0°C / 86.0°F | 30.2°C / 86.4°F | 30.6°C / 87.0°F |
| July | 29.6°C / 85.3°F | 29.8°C / 85.7°F | 30.0°C / 86.0°F |
| August | 29.5°C / 85.1°F | 29.8°C / 85.7°F | 30.3°C / 86.5°F |
| September | 29.4°C / 84.9°F | 29.6°C / 85.2°F | 29.8°C / 85.6°F |
| October | 29.0°C / 84.1°F | 29.5°C / 85.1°F | 29.9°C / 85.9°F |
| November | 28.5°C / 83.2°F | 28.9°C / 84.0°F | 29.3°C / 84.8°F |
| December | 27.7°C / 81.8°F | 28.0°C / 82.5°F | 28.6°C / 83.4°F |
| Month | Min | Avg | Max |
|---|---|---|---|
| January | 26.5°C / 79.7°F | 26.8°C / 80.2°F | 27.0°C / 80.5°F |
| February | 26.7°C / 80.0°F | 27.0°C / 80.6°F | 27.2°C / 81.0°F |
| March | 27.4°C / 81.3°F | 27.8°C / 82.0°F | 28.1°C / 82.5°F |
| April | 28.1°C / 82.6°F | 28.6°C / 83.4°F | 28.9°C / 84.1°F |
| May | 28.3°C / 82.9°F | 28.8°C / 83.8°F | 29.1°C / 84.4°F |
| June | 28.0°C / 82.3°F | 28.6°C / 83.4°F | 29.0°C / 84.2°F |
| July | 27.7°C / 81.8°F | 28.3°C / 82.9°F | 28.8°C / 83.8°F |
| August | 27.5°C / 81.4°F | 28.1°C / 82.6°F | 28.6°C / 83.5°F |
| September | 27.3°C / 81.1°F | 27.8°C / 82.0°F | 28.1°C / 82.6°F |
| October | 26.8°C / 80.3°F | 27.3°C / 81.2°F | 27.7°C / 81.8°F |
| November | 26.6°C / 79.9°F | 27.1°C / 80.7°F | 27.2°C / 81.0°F |
| December | 26.6°C / 79.8°F | 26.9°C / 80.5°F | 27.1°C / 80.7°F |
5-year averages (2021–2025). Min/Max are typical daily lows and highs, not record extremes. (Copernicus ERA5)
Koh Samui holidays
Koh Samui is an island in the Gulf of Thailand, off the coast of Surat Thani province, with palm-fringed beaches around a hilly, forested interior and a ring road that circles it in about 50 km. It is a major tourism centre in the Gulf of Thailand, with its own airport and a wide range of accommodation, and most visitors rent a car or scooter to reach its beaches, waterfalls and temples.
Beaches
Chaweng, on the east coast, is Koh Samui's longest and busiest beach, lined with hotels, bars and restaurants, with calm water in the dry season. Lamai, to the south, is a little quieter and ends at the Hin Ta Hin Yai rocks. Between the two, Coral Cove is a small bay of sand and granite boulders with snorkelling off the rocks, and Silver Beach, also called Thong Takhian or Crystal Bay, is the next cove to the south. In the north, Bophut, Maenam and Choeng Mon are quieter beach bases, though water depth and swimming conditions vary from beach to beach and with the weather. We measure the sea temperature shown on this page near the beach at Coral Cove.
Things to do
The Big Buddha, at Wat Phra Yai on an islet joined to the north-east tip of Koh Samui by a causeway, is Koh Samui's best-known landmark, and nearby Wat Plai Laem has a many-armed statue of the goddess Guanyin over a lake. Fisherman's Village in Bophut has old wooden shophouses and evening market stalls; check current market days locally. Na Muang waterfalls are in the south of the island, and day trips by boat visit the islands of Ang Thong National Marine Park, as well as Koh Phangan and Koh Tao.
Weather and best time to visit
At Koh Samui the sea stays above 27 °C / 81 °F all year, even in the coolest month.
Koh Samui has a different season from Phuket and the Andaman coast: the wettest months are usually from about October to December, when the north-east monsoon brings heavy rain, while late winter and spring are generally drier, and the summer months bring sunshine mixed with showers. Christmas and New Year, the drier months and the July and August holidays are the busiest times on Koh Samui, and accommodation prices vary with the dates.
Hotels and where to stay
Chaweng is the liveliest area of Koh Samui, with the most hotels and nightlife; Lamai is calmer, Bophut and Fisherman's Village suit couples, and Maenam and Choeng Mon have quieter beach resorts.
Signature hotels: W Koh Samui · Centara Reserve Samui · SALA Samui Chaweng Beach Resort
Airport and getting there
Samui International Airport (USM), in the north-east of Koh Samui, has flights from Bangkok, about an hour away, and from several other Asian cities; the drive to Chaweng takes about 10 to 15 minutes. Car and passenger ferries also cross from Donsak pier near Surat Thani, and boats connect Koh Samui with Koh Phangan and Koh Tao.