In principal there are 2 seasons: dry and wet, with each a hot and cool period. Cambodia has a dry period, from December(cool) to May(hot), with temperatures to 35° degrees Celsius (April) and a rainy period, from June(hot) to November(cool), when heavy rain showers can be expected.
Cambodia is a relatively small country; temperatures do not vary much throughout, except in the cooler north.
Cambodia enjoys sun true out the year, even in rainy season. It can rain very heavy for a few hours followed by a clear sky with sun.
From December to March is the tourist high season – it can get pretty crowded. June to September sees cooler temperatures with more chance of rain, but it’s not as busy.