Phnom Penh, the capital of Cambodia, sits at the confluence of the Mekong and Tonlé Sap rivers on a low, flat plain in the south of the country, at approximately 11.56°N, 104.92°E. It has a tropical savanna climate (Köppen Aw) — hot and humid year-round — with a monsoon-driven wet season and a hot, dry season, and no cool season at all.

There is no summer in the temperate sense: temperatures stay hot year-round, with daytime highs around 32–35°C. The hottest months come just before the rains, in March and April, when highs can exceed 35–38°C with punishing humidity. The southwest monsoon then brings the wet season from May to October, with heavy afternoon and evening downpours and thunderstorms, peaking in September and October.

There is no true winter, but the dry season from November to February is the most comfortable time, with warm days around 30–32°C, cooler nights near 21–23°C, lower humidity and little rain, as the dry northeast monsoon blows. This bright, drier, milder stretch is comfortably the best time to visit the city.

Phnom Penh receives on the order of 1,400–1,500 mm of rain a year, overwhelmingly concentrated in the wet season from May to October, with September and October the wettest, while December to February is nearly rainless. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Phnom Penh sits at a hydrological marvel: during the monsoon the swollen Mekong forces the Tonlé Sap river to reverse its flow, backing up into the great lake and swelling it several times over, before it drains again as the rains end — a reversal celebrated each November at the Water Festival. Wet-season flooding remains a serious risk on the low plain.

To follow any single measurement in Phnom Penh more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.