September in Cambodia tends to be wet and warm with high levels of rainfall and average temperatures of 26°C. When it rains it is usually for a few hours rather than all-day downpours, although these can also happen. It's a great month to travel to Cambodia if you're keen to avoid the crowds and are happy to take your chance with rainfall.
Across the country the flora and fauna is in bloom, rice paddies are green and lush. The moats and pools that surround the Angkor temples are full, which makes for some perfect photo opportunities of temple reflections in the water.
Another benefit of travelling in Cambodia at this time is that crowd numbers at the temple sites are much lower and at some of the outlying temples you may well have the place to yourself. A thunderstorm whilst exploring the Angkor temples can be a memorable experience!
September is a great time of year to visit the flooded forests and floating villages of Tonle Sap Lake, as it swells to more than 5 times its size during wet season.
On the south coast and in more rural regions, such as Ratanakiri, rainfall can be heavier and more prolonged although dry days are still expected. Due to the rain of the past few months, some more rural roads could have become difficult to travel however they are few and far between.