Koh Rong in September
September is still very wet, although the rain starts to ease slightly compared with August.
| Average daytime high | 30 °C |
| Average night-time low | 23 °C |
| Average rainfall | 487 mm |
| Average sea temperature | 28.8 °C |
Long-term averages for nearby Sihanoukville: World Meteorological Organization 1982-2024; sea temperature: seatemperature.org.
Weather
Expect frequent showers and high humidity. Daytime highs are around 30°C, the lowest of the year.
Sea and activities
The sea can still be rough on some days. Plan boat trips for calmer mornings.
Holidays and crowds
Pchum Ben, an important Cambodian festival, falls in late September or October depending on the lunar calendar (10-12 October in 2026).