Ko Samui in September usually sees fair weather conditions, with an average daily high temperature of +81°F and roughly 0 sunny days. However, you should prepare for about 17 rainy days with an average precipitation of 142 mm. The weather is changeable so pack for every eventuality. Search flightsin one click on Avionero.
Average weather
☀️
+81°F
Avg. max. temperature
+70°F
Min.
+90°F
Max.
142 mm
Total precipitation
79%
Avg. humidity
3 m/s
Avg. wind
0 ☀️
Sunny Days
2 ⛅️
Cloudy
17 🌦
Rainy
Our opinion: Ko Samui has OK weather in September.
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Average temperature in Ko Samui in September
Here are the expected maximum, average and minimum temperatures in Ko Samui for September based on the historical data.
Last Year
Historical Data
The temperature in September is +81°F on average, with a range between a maximum of +82°F during the day and a minimum of +75°F at night.
The average maximum temperature goes up 25% by the end of the month, compared with the beginning of the month, from +79°F to +81°F.
Is Ko Samui warm or cold in September?
Ko Samui is typically warm in September.
Maximum temperatures go up compared to the previous month from +81°F to +81°F. The minimum temperature also goes down from +77°F to +75°F.
It’s generally warm, but pack a long-sleeve shirt for evenings.
September is one of the warmest months in Ko Samui, here is the comparison with other months:
Water temperature in Ko Samui in September
Water in Ko Samui in September is Very warm. It varies from +83°F to +86°F, with an average of +84°F.Note that the air temperature is lower than the water temperature, averaging around +81°F.
In September, water temperatures are average relative to the rest of the year:
The warmest water temperatures in Ko Samui are reached in May, when the average sea temperature rises to +86°F. The coldest water temperatures are in January, with an average of +82°F.
Can you swim in Ko Samui in September?
You can definitely swim in Ko Samui in September, the water is very warm (+84°F in average), and might even be unpleasant for ones who like it more fresh.
🦭
Cold
Below +61°F
🏄♂️
Fresh
61°F - 70°F
🏊
Comfortable
70°F - 77°F
👙
Warm
77°F - 82°F
🔥
Very warm
+82°C and up
Don't forget sunscreen and a hat, it's going to be hot!
Climate in Ko Samui in September
Ko Samui weather looks like this, on average, in September and the surrounding months.
August
September
October
Avg. temperature
+81°F
+81°F
+79°F
Min. temperature
+68°F
+70°F
+70°F
Max. temperature
+91°F
+90°F
+90°F
Rainfall
85 mm
142 mm
242 mm
Wind
3 m/s
3 m/s
2 m/s
Avg. water temperature
+84°F
+84°F
+85°F
Humidity
78%
79%
82%
Air pressure
1008 HPa
1008 HPa
1009 HPa
Sunny days
0
0
0
Cloudy days
4
2
2
Rainy days
18
17
16
Snowy days
0
0
0
September weather is still as ok as in August.The temperature levels stay the same in the area of +81°F for average maximum temperature during the day.Prepare for more rain. Average rainfall goes from 85 mm to 142 mm.Humidity rises from 78% to 79%.The average wind speed doesn’t change much during September, staying around 3 m/s.The amount of sunny days stay about the same, averaging 0 sunny days during the month.
October brings much the same weather, it remains ok.
Wind speed in Ko Samui in September based on historical data.
Last Year
Historical Data
The average wind speed is 3 m/s getting up to 5 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in Ko Samui is gradually decreasing during September, going from 5 m/s to 1 m/s over the course of the month.
Rain
Amount of rainfall in mm during September in Ko Samui based on historical data.
Last Year
Historical Data
A chance of rain on a typical day in September stands at 80%, leading to total precipitation of around 198 mm. The maximum amount of rainfall per day is around 30 mm, which is moderate rain.September is a pretty wet month with over 24 rainy days, so don’t forget to pack an umbrella, raincoat, and a pair of wellies.
September is one of the rainiest months in Ko Samui, here is a comparison with other months, total mm:
Ko Samui wettest month is November, where a typical day has a 57% chance of precipitation and 278 mm of rainfall per day. February, on the other hand, is the driest month with a mere 38% chance of precipitation and 29 mm of rainfall per day.
How was the weather last September in Ko Samui?
This is the weather in Ko Samui in September 2023:
1 September
🌧️
+79°F
2 September
🌧️
+78°F
3 September
🌧️
+79°F
4 September
🌧️
+79°F
5 September
☀️
+80°F
6 September
☁️
+82°F
7 September
☀️
+81°F
8 September
☀️
+80°F
9 September
☁️
+81°F
10 September
🌧️
+79°F
11 September
☁️
+79°F
12 September
☁️
+79°F
13 September
☀️
+81°F
14 September
🌧️
+79°F
15 September
🌧️
+80°F
16 September
🌧️
+79°F
17 September
☁️
+79°F
18 September
☀️
+81°F
19 September
☀️
+81°F
20 September
☀️
+81°F
21 September
🌧️
+79°F
22 September
🌧️
+80°F
23 September
🌧️
+79°F
24 September
🌧️
+81°F
25 September
🌧️
+79°F
26 September
🌧️
+79°F
27 September
🌧️
+78°F
28 September
☁️
+80°F
29 September
☀️
+81°F
30 September
☀️
+81°F
In September 2023 Ko Samui had 9 sunny days, 6 cloudy days, and 15 rainy days. The average maximum temperature was +81°F, with an absolute maximum of +82°F and a minimum of +77°F. The average humidity was 82%, with a maximum of 100% and a minimum of 69%. The average wind speed was 3 m/s, with a maximum of 10 m/s and a minimum of 0 m/s.
Are you planning a trip in September?
Climate Change Over the Years
This is how Ko Samui climate has changed over the last 43 years.
The climate in Ko Samui in September has not changed that much over the last 43 years.
The average temperature was the lowest in 1986 (+79°F) and the highest in 2012 (+83°F). The driest year was 1997 with only 927 mm of rainfall, and the wettest year was 1999 with 1981 mm.
FAQ
Frequently asked questions about the weather in Ko Samui in September:
Is September a good time to visit Ko Samui?
It’s always a good time to visit Ko Samui, but the weather is changeable in September, so plan a mix of indoor and outdoor activities and exploring, and pack for every eventuality.
Can you sunbathe in Ko Samui in September?
September is warm in Ko Samui. You may enjoy some beach or pool time in the day, but pack something a tad warmer for the evening.
Can you swim in Ko Samui in September?
Yes, you can swim in Ko Samui in September, the water is very warm, with temperature averaging at +84°F, but it's important to manage hydration and sun exposure.
Is Ko Samui rainy in September?
Ko Samui is often rainy in September. You may get a bit damp when outside, so pack an umbrella, and maybe even a raincoat.
Is it sunny in Ko Samui in September?
Usually, it’s not very sunny in Ko Samui in September, often it’s pretty cloudy. Pack for any eventuality; layering can help reduce the number of bulky items needed.
Other cities in Thailand
Check out the weather for other cities in Thailand.
For this page, we’ve looked at the typical weather in Ko Samui, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.
