Ko Samui Weather in September

September in Ko Samui brings high temperatures around 30°C (86°F) during the day, dropping to 27°C (81°F) at night, with quite a bit of rainfall expected, averaging around 138 mm (5.4 in) for the month.

Rainfall in Ko Samui in September

This month experiences about 18 days of rain according to historical data, averaging 138 mm (5.4 in). Expect frequent rainfall this month, and not just light drizzle. When it rains, it tends to come down hard.

Temperature in Ko Samui in September

If you're visiting Ko Samui in September, expect highs of 30°C (86°F) and overnight lows around 27°C (81°F). Conditions stay fairly consistent through the month, making it easier to plan what to wear. Nights are warm at 27°C (81°F), which can make sleeping uncomfortable. Keeping windows open or using a fan can help. A cold shower before bed is also a good way to cool down.

Sunshine in Ko Samui in September

The city usually sees around 145 hours of sunlight, indicating a moderately sunny period.

Average water temperature in September

The water is 29°C (84°F) — very warm by most standards. Comfortable to swim in, but not particularly refreshing if you're looking to cool off.

If you prefer dry days with pleasant temperatures, January and February typically offer the best circumstances. If you're seeking pleasant, dry and sunny weather somewhere else in the world, our weather planner can help you explore other options.

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For a detailed overview over the year and the best time to visit Thailand, check out our Ko Samui's climate page.

Ko Samui Temperature in September

Min Temperature 27°C (81°F)  

Max Temperature 30°C (86°F)  

Water Temperature 29°C (84°F) *  

Chance of Rain 59%  

Precipitation 138 mm (5.4 in)  

Rainy days 18 days  

Humidity 79% *  

Sunshine 145 hours *  

Percentage Sunshine *  

* Data from: Koh Samui, Thailand (19 KM, 12 Miles).

What to Wear in Ko Samui in September

Warm weather calls for comfortable, breathable clothing in September. Cotton t-shirts, shorts, light dresses, and sandals are perfect. You might still want a light layer for evenings or air-conditioned places (for example buses). High rain levels are expected, so pack waterproof gear and an umbrella or poncho. Expect water temperatures of around 29°C (84°F), which is ideal for taking a refreshing dip. Bring swimwear and consider packing a towel for drying off. Bring sunglasses since you'll have some sunny periods throughout the month

What To Do in Ko Samui in September

We rated the following activities from 1 (least suitable) to 10 (best) to do.

Swimming

7/10

Cycling

7/10

Walking

7/10

Camping

7/10

Outdoor sports

7/10

Select a Month

Check the conditions for any month of the year.

• January
• February
• March
• April

• May
• June
• July
• August

• September
• October
• November
• December

For a detailed overview over the year and the best time to visit Thailand, check out our Ko Samui's climate page.

More climate data for Ko Samui

Temperature Rainfall Sunshine Humidity Water Temp

See the full Ko Samui climate overview or explore weather in Thailand.