What is Koh Samui like in September?

Weather

September is a good month for weather on Koh Samui, with plenty of sunshine and warm days. Highs are around 31°C and the sea is around 29°C.

Rain becomes more likely as the month goes on. When it comes, it is usually in the afternoon, and the showers tend to be short, with the sunshine returning after an hour or two. You may also get the odd overcast day.

It is not a dry month on paper. Weather records show some rain on more than half the days of September, though most of it is brief, so pack for the occasional shower rather than expecting every day to be clear.

On a mid-September day the sun rises at about 6:09am and sets at about 6:20pm. Times are from timeanddate.com (Na Thon, Koh Samui).

Keep in mind: Koh Samui has a tropical climate, and the weather can change quickly. Treat these patterns as a guide rather than a forecast, and check the forecast closer to your dates.

If it rains

Afternoon showers are the usual pattern, so plan outdoor time for the morning and keep the afternoon flexible.

A Thai cooking class is a good option whatever the weather, and many classes include hotel pickup and a visit to a local market. Book a Thai cooking class in Koh Samui →

Central Samui is the easy choice with children. It is air-conditioned and has play areas, and for more ideas for families, see our guide to what to do in Koh Samui with kids on a rainy day.

Crowds and deals

September is quieter than July and August. The school holiday crowds have gone, and the island feels calmer as the month goes on.

In our experience, accommodation deals are usually better later in the month.

If you want a quieter island, you are not tied to school holidays and you want a good chance of sunshine, September is a good time to visit Koh Samui.