Avg weather in September
12 Hrs per day
199 mm per month
89 % avg
3 Mph avg


What’s the weather like in Thailand in September?

Thailand’s climate’s largely tropical as the country’s close to the equator, which means you’ll get lots of hot weather in September. There’s some differences across regions and points of interest to keep an eye out for though.

Regional variations

Southern Thailand has a fairly typical tropical climate, with things getting more equatorial the further south you go, which means there’s higher heat and humidity. There’s similar temperatures all year round in southern and central regions, while you’ll get more rain in mountainous areas. The two monsoon seasons have a big impact on the weather, with November to April’s north eastern monsoon bringing drier weather than May to October’s south western monsoon, which brings warmer, cloudier and more humid conditions.


Koh Samui in the Gulf of Thailand’s one of Thailand’s most famous destinations, and has a year-round season. You’ll get an average high of 31ºC in September, with things staying warm at night. The sea’s perfect for swimming with a lovely temperature of 29ºC, while humidity’s very high. Average rainfall’s 130mm over 11 rainy days, and you can expect six hours of sunshine from the 12 hours of daylight each day. Wear sun cream in the sun as UV levels are extreme. The sun goes down at around 6.15pm through most of September.

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