Koh Rong in September
Last fact-checked: October 2026. Climate figures are long-term averages for nearby Sihanoukville.
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).
Best Beaches & Coast Conditions in September
East & South-East Coast beaches (Long Set, Pagoda, Coconut Beach) offer the most sheltered water while the southwest monsoon gradually begins to weaken late in the month.
- Recommended Activities: Lush forest walks, full waterfalls, quiet mangrove kayaking at Prek Svay and Prek Ta Sok, and atmospheric photography during Pchum Ben.
- What to Pack & Booking Tip: Light rain gear, waterproof phone pouch, coconut oil against sandflies after rain, and USD cash.
Koh Rong Weather in September: FAQ
What is Pchum Ben in September / October?
Pchum Ben is Cambodia's 15-day Ancestors' Festival. Many locals visit pagodas (including Koh Rong's island pagoda) with offerings, and the final 3 public holidays bring domestic travelers to the coast.
Is September a quiet time on Koh Rong?
Outside the 3-day Pchum Ben holiday, September is one of the quietest, most peaceful months on the island with very low hotel prices.
How warm is the water in September?
The sea averages a comfortable 28.8 °C (84 °F).