The short answer
November to February is the best weather of the year: dry, sunny, and cool enough at dawn to want a layer. It is also the busiest and the most expensive. March to May is dry but seriously hot. June to October is the green season — daily rain, dramatic skies, half the visitors and noticeably lower room rates.
If you can only go once and want the easiest trip, come in December or January. If you have travelled in the tropics before and want the country closer to itself, come in September or October.
The two seasons
The south-west monsoon brings the rains from roughly May to October. Cambodian rain is rarely all-day drizzle — it is usually a heavy, theatrical downpour in the late afternoon that clears within an hour or two. Mornings are frequently fine.
The pay-off is the landscape. Rice paddies flood emerald green, the moats at Angkor fill and reflect the towers, the Tonlé Sap swells to several times its dry-season size, and waterfalls in Mondulkiri and Ratanakiri actually run.
The cost is mud on unsealed roads in the north-east, occasional ferry cancellations to the islands, and mosquitoes.
Month by month
| Month | Weather | Crowds | Notes |
|---|---|---|---|
| November | Dry, 22–31 °C | Building | Arguably the perfect month. Water Festival falls here. |
| December | Dry, cool mornings | Peak | Best light at Angkor. Book well ahead. |
| January | Dry, 21–31 °C | Peak | Coolest month. Highland nights genuinely chilly. |
| February | Dry, warming | High | Still excellent. Prices start easing late in the month. |
| March | Hot, 24–35 °C | Moderate | Temples are hard work after 10 am. |
| April | Hottest, 35 °C+ | Moderate | Khmer New Year — much of the country stops. |
| May | First rains | Low | Humid, but the landscape starts turning green. |
| June | Wet, warm | Low | Good value. Afternoon storms. |
| July | Wet | Low | Countryside at its greenest. |
| August | Wet | Moderate | European summer brings a small bump in visitors. |
| September | Wettest | Lowest | Heaviest rain, emptiest temples, best photographs. |
| October | Rain easing | Low | Pchum Ben. Waterfalls at full power. |
Festivals worth planning around
- Khmer New Year (Choul Chnam Thmey) — mid-April, three days. Joyful, water-throwing, and much of the country shuts down and travels home. Transport is packed; book everything early.
- Pchum Ben — around September or October, fifteen days honouring ancestors, with the final days most significant. Businesses close and pagodas fill.
- Water Festival (Bon Om Touk) — November, marking the reversal of the Tonlé Sap's flow. Boat races on the Phnom Penh riverfront draw enormous crowds.
These follow the lunar calendar, so dates move year to year.
Regional differences
The coast and islands track the monsoon most sharply. November to April is calm and clear; June to September brings choppy crossings and some island resorts close entirely.
Koh Kong is the wettest province in the country — the green season there is genuinely wet.
Mondulkiri and Ratanakiri sit higher and cooler. January nights need a jumper. The red laterite roads turn to deep mud from July to September, which limits how far you can get.
Angkor is worth a specific note: the moats and barays are full and reflective from about September to January, and drop away through the dry season.