Cambodia's climate is tropical, with high temperatures, and two distinct seasons: a monsoon-driven rainy season (May‐October) with south-westerly winds ushering in clouds and moisture that accounts for anywhere between 80-90% of the country’s annual precipitation, and a dry season (November-April), with cooler temperatures, particularly between November and January. Average temperatures are relatively uniform across the country, but are highest in the early summer months before the rainy season begins, when maximum temperatures often exceed 32°C. Temperatures remain between 25-27°C throughout the rest of the year. The wet season arrives with the summer monsoon, in May through November, bringing the heaviest rainfall to the southeast and northwest. The annual average rainfall is typically 1,400-2,000 mm with higher rates in the coastal and highland areas and lower rates in other inland regions. Inter‐annual variations in climate result from the El Niño Southern Oscillation, which influences the nature of the monsoons in the region. El Nino events generally bring warmer and drier than average winter conditions across Southeast Asia, while La Niña episodes bring cooler than average conditions.
- Temperatures in Cambodia are generally consistent throughout the year, averaging between 25℃ and 27℃. Average maximum temperatures can reach 38℃(April) and average minimum temperatures reaching 17℃.
- Temperature increases have been observed, with an approximate increase of 0.18℃ per decade since the 1960s.
- Temperature increases have increased most rapidly during the country’s dry season (November to April), increasing by 0.20℃ to 0.23℃ per decade. Temperatures have increase during the rainy season (May to October), but not as significantly, with increases between 0.13℃ and 0.16℃ per decade. The number of ‘hot days’ in the country has increased over the last century, by as much as 46 days per year.
- Rainfall in Cambodia varies widely across the country.
- Average annual rainfall can be as low as 1,400 mm in the central lowlands and as high as 4,000 mm near the Cardamom mountains and nearby coastal areas in the southwest.
- The country’s eastern plains receive approximately 2,000 to 2,600 mm of rainfall annually and may exceed those amounts in the mountainous areas in the Northeast.
- While rainfall was observed to increase in some areas since the 1960s, no statistically significant changes were detected over the 20th century, either in terms of annual rainfall or extreme events.
- Precipitation variability is linked to the El Niño Southern Oscillation phenomenon, with years of strong El Niño correlated with years of moderate and severe drought over the 20th century.