Is the weather good in Thailand in September 2025?
For the past few decades, the average daily temperatures in Thailand during September have been around +86°F.
In Thailand the temperature rarely varies more than seven degrees between the different parts with the highest temperature +86°F in Chiang Mai to +81°F in Ko Samui. So you should be able to pack for similar conditions wherever you go in the country.
Temperature, wind and humidity in September
- rainiest? Trat, with an average of 18 mm of rain and humidity of 86%;
- warmest? Chiang Mai, with daytime temperatures averaging +90°F;
- windiest? Ko Samui, with an average of 3 m/s;
- coolest? Ko Samui, with daytime temperatures averaging +81°F;
How good is the weather in Thailand in September?
How warm is it in Thailand during September?
This is how hot it usually is in September
- Average maximum temperature for the month: +86°F;
- Average minimum temperature for the month: +77°F;
- Highest monthly temperature: +86°F;
- Lowest monthly temperature: +77°F;
Monthly temperatures:
- Warmest: March with an average +90°F during the day;
- Coldest: January with an average +84°F of the day;
- Hottest month in hottest city: April in Chiang Mai;
- Coldest month in coolest city: January in Ko Samui;
Can you swim in Thailand in September?
Winds in Thailand during September
September tends to offer light winds averaging 2 m/s. However, coastal cities may experience breezes during the mornings and afternoons.
Comparison between cities in September:
- Highest average wind speed: Ko Samui with 3 m/s;
- Lowest average wind speed: Bangkok with 1 m/s;
- Windiest day of the month: Ko Samui with 3 m/s;
- The least windy day of the month: Chiang Mai with 0 m/s;
Humidity and precipitation in Thailand in September
Comparison between cities in September:
- Highest average rainfall: Trat with 545 mm;
- Lowest average rainfall: Ko Samui with 142 mm;
- Most number of rainy days: Trat with 30 rainy days;
- Least number of rainy days: Bangkok with 15 rainy days;
- Highest risk of rain during the day: Trat with 100%;
- Least risk of rain during the day: Bangkok with 50%;
- Highest average humidity: Trat with 86%;
- Lowest average humidity: Bangkok with 79%;
Tips for traveling to Thailand in September
Looking for some tips for traveling to the sun, snow, or whatever you're aiming for Thailand? Activities, weather, and clothing are closely linked. In addition, it's important to pack only what you really need so you don't have to worry about heavy packing or paying extra baggage fees.
Here is some advice on what to pack and what kind of activities you can do in the Thailand based on the weather that September is expected to bring. The advice applies to the country as a whole – local weather and possible activities may differ somewhat.
Pack right for September
- For light showers, an umbrella or a thin and light rain cape is usually sufficient, while more rain may require rainwear and rain boots.
- Warm - neither hot nor cool, are probably the most comfortable when you think of sunbathing. Shorts, shorter skirts or dresses, tank tops and t-shirts are the basics here. If you're going to a seaside resort, don't forget your swimwear and maybe even a snorkel, mask and flippers.
- Light winds are probably most comfortable in hot weather but is cooling in cool and cold weather. If it is hot (when the air temperature is about 30 degrees), the wind can have a warming effect. A thin, windproof jacket and long trousers help to counteract these effects.
- High humidity means that the air conducts heat to and from the skin more easily. For example, if the air is hot (above skin temperature), it will be harder to stay cool. On the other hand, if the air is cool or cold, it is more difficult to stay warm. In high humidity, the choice of clothing makes less of a difference. However, your physical activity plays a bigger role.
FAQ
What can you do outside when it's warm in Thailand?
Is September a good time to visit Thailand?
Monthly weather in Thailand
Source of the data
For this page, we’ve looked at the typical weather in Thailand, 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.