Thailand Weather in September: Climate, Tips and Best Destinations
September in Thailand is the peak of the rainy season: hot and humid, frequent showers, but also lush green landscapes and budget-friendly prices.
General Climate in September
September is typically the wettest month in Thailand, especially along the Andaman coast and in central and northern regions. Some years can be extremely rainy. Rainfall intensity varies widely between the North, South, and Central plains, as well as between the Gulf of Thailand and the Andaman coast.
Average national temperatures hover around 26 °C, with highs ranging from 24–32 °C depending on the region.
Temperatures, Rainfall & Humidity by Region
Bangkok & Central Thailand
- Temperatures between 25–32 °C.
- Monthly rainfall 220–280 mm, with many rainy days.
- Typical day: high ~31 °C, low ~25 °C, humidity ~78%.
- Cloudy skies dominate, about 90% overcast.
Northern Thailand (Chiang Mai…)
- Temperatures 23–31 °C.
- Rainfall around 180–250 mm.
- Cooler nights, lush scenery, perfect for waterfalls and national parks.
Andaman Coast (Phuket, Krabi…)
- Temperatures 24–31 °C, very heavy rainfall 300–400 mm.
- Phuket average: ~388 mm of rain, ~21 rainy days.
- Rough seas, limited water activities.
Gulf Islands (Koh Samui…)
- Drier: 100–160 mm of rain.
- Highs around 31 °C, sea ~29 °C.
- About 11 rainy days and 6 hours of sunshine per day.
- Best area for beach holidays in September.
Why Travel in September? Pros & Cons
Advantages
- Lush greenery and vibrant landscapes.
- Fewer tourists and lower prices (up to 50% off hotels).
- More authentic atmosphere at cultural sites.
Drawbacks
- Afternoon and evening showers, sometimes heavy.
- Rough seas on the Andaman side, possible ferry cancellations.
- Need for a flexible travel plan.
Practical Travel Tips for September
- Bring rain gear (poncho, umbrella, non-slip shoes).
- Favor Gulf islands (Koh Samui, Koh Phangan) for better chances of sunshine.
- Plan outdoor activities in the morning before afternoon showers.
- Explore cultural sites (temples, museums, markets) in Bangkok and Chiang Mai.
- Follow local weather forecasts and adjust accordingly.
- Take advantage of promotions on flights and hotels.
Historical Weather Data (Phuket 2009–2022)
| Year | Avg. Temp. | Rainfall (mm) | Rainy Days |
|---|---|---|---|
| 2009–2022 avg. | ~27–28 °C | ~300–400 mm | 19–25 days |
👉 In Phuket, historical data shows an average of 27 °C in September, with 388 mm of rain and about 21 rainy days.
