Thailand weather in September
In September, Thailand averages 29 to 31°C by day across Phuket and Bangkok. Bangkok is the warmest at 31°C, Phuket the coolest at 29°C. The sea is 30°C.
Thailand in September, place by place
Warmest first. Anywhere at 24°C or more is proper beach weather. Tap a place for its full September detail.
Heading to Thailand in September?
Share the places you've saved on TikTok and Instagram for Thailand to Dream Trip. It pins them on a map and builds your days around them.
Thailand in September: quick answers
Is Thailand hot in September?
In September, Thailand averages 29 to 31°C by day across Phuket and Bangkok. Bangkok is the warmest at 31°C, Phuket the coolest at 29°C. The sea is 30°C. September is hot but wet in Bangkok: rainy season, so pack for showers.
Where is warmest in Thailand in September?
Bangkok, at an average high of 31°C. The driest is Phuket, with about 243 mm of rain.
Can you swim in the sea in Thailand in September?
Yes: Phuket (30°C) has sea temperatures of 21°C or more, comfortable without a wetsuit.
How we measured this
Thailand here means Phuket and Bangkok: the places we measure. Figures are averages of every day from 2016 to 2025 from the Open-Meteo historical weather archive (ECMWF ERA5); sea temperatures are 2023 to 2025 averages. Rain is the average monthly total, and 150 mm or more counts as rainy season.
Planning Thailand in September?
Save the places you find on TikTok and Instagram for Thailand to one map, and Dream Trip turns them into a day-by-day plan.
