Sea Temperature around Koh Samui

Summary

The sea around Koh Samui stays warm all year, roughly 28-30°C. The warmest water is usually April to June (around 30°C) and the coolest, if you can call it that, is December to February (around 28°C). You never need a wetsuit for swimming; a rash guard is useful for sun and jellyfish protection.

Typical range

28-30°C year-round

Notes

• Swimming is possible all year, but sea conditions (waves, currents, jellyfish) matter more than temperature.
• Water clarity is usually best in the February-April window.