Koh Samui Weather

February is one of Koh Samui's best months — peak dry season with hot, sunny days and the lowest rainfall of the year (around 60mm). It averages 30°C/24°C. This is prime time: calm, clear seas make Ang Thong, Koh Phangan, and Koh Tao trips reliable and beautiful, with excellent snorkeling and diving visibility. Humidity dips a touch below the year's norm, so the heat feels more comfortable than the muggier months. Because it's peak season, expect higher prices and busy beaches in Chaweng and Bophut — book 2-3 months ahead. Chinese New Year (date varies) brings a wave of regional visitors and a short price bump. Remember the Gulf timing: February is fantastic on Samui and also great on the Andaman coast (Phuket/Krabi), so it's a strong all-Thailand month — but Samui's window is shorter, peaking now through April. The sea is a warm ~29°C with the best clarity of the year. UV is extreme (11) — reapply SPF 50+ and limit midday sun.

March is another of Koh Samui's best months — dry, sunny, and hot, with low rainfall (around 75mm). It averages 31°C/25°C, a touch warmer than February. Seas stay calm and clear, so Ang Thong, Koh Phangan, and Koh Tao trips are reliable with great snorkeling and diving. This is the heart of the dry window (mid-January to April) and a strong all-round month for beaches and island-hopping. Mango season gets going — the mango sticky rice is at its best now through June. It's still peak season, so prices and crowds are high, though slightly past the February-Chinese New Year peak. The heat is building toward April's hottest stretch, and UV is extreme (12) — limit midday sun, hydrate, and reapply SPF 50+. The sea is a warm ~29°C with excellent clarity. As with the rest of the dry season, both Samui (Gulf) and the Andaman coast are good now, so it's a flexible month for combining Thai destinations.

January is the transition from Koh Samui's wet season into its best dry window. It averages 29°C/24°C with rainfall easing through the month (around 180mm, front-loaded early). Early January can still see leftover northeast-monsoon showers, but from mid-to-late January the skies clear, the seas calm, and boat trips to Ang Thong, Koh Phangan, and Koh Tao become reliable again. Late January is genuinely excellent. Note the Gulf timing: while Phuket and Krabi on the Andaman coast are in peak dry season, Samui is just emerging from its wettest stretch — the two coasts run opposite monsoons. The New Year period (early January) is a yearly travel peak with the highest hotel prices; book Christmas/New Year 4-6 months ahead. Prices ease a little once the holidays pass, making late January good value with improving weather. The sea stays a warm ~29°C year-round, so swimming is fine throughout — it's clarity and calm seas, not water temperature, that improve in the dry season.