Phnom Penh records about 900mm of rain across roughly 96 wet days a year, which is a 26% chance on an average day. September is the wettest month at 129mm (14% of the annual total) and January the driest at 21mm. Local rain type: steady rain.
Chance of rain on an average day: 26%
Rainfall climatology for Phnom Penh. The live hour-by-hour answer for today loads at the top of this page from Open-Meteo and refreshes through the day — the figures below describe a typical year, not today.
Last updated: · Live forecast data refreshes hourly.
| Annual rainfall | 900mm |
| Rain days per year | 96 |
| Odds on an average day | 26% |
| Wettest month | September — 129mm over 14 days |
| Driest month | January — 21mm over 2 days |
| Rain type | steady rain |
| Best dry window | January is the most reliable dry stretch of the year. |
| Worst rain window | September carries the highest chance of a washed-out day. |
September delivers 514% more rain than January (129mm vs 21mm). That gap is the difference between planning around showers and ignoring them.
No single month holds more than 14% of the annual total, so rain in Phnom Penh is spread through the year — there is no season you can rely on being dry.
Phnom Penh rain typically comes as discrete showers, so a compact umbrella and a flexible plan are usually enough.
Rain falls on about 14 days in September against 2 in January — the frequency swing matters more for planning than the millimetre totals.
Climate normals. Use them to judge whether today's live forecast at the top of the page is typical or unusual for the season.
| Month | Rainfall | Rain days | Chance on a given day | Highs |
|---|---|---|---|---|
| January | 21mm | 2 | 7% | 32°C |
| February | 21mm | 2 | 7% | 32°C |
| March | 39mm | 4 | 13% | 33°C |
| April | 57mm | 6 | 20% | 34°C |
| May | 75mm | 8 | 27% | 34°C |
| June | 93mm | 10 | 33% | 35°C |
| July | 111mm | 12 | 40% | 35°C |
| August | 129mm | 14 | 47% | 35°C |
| September | 129mm | 14 | 47% | 34°C |
| October | 111mm | 12 | 40% | 34°C |
| November | 75mm | 8 | 27% | 33°C |
| December | 39mm | 4 | 13% | 32°C |
Rain probability is the chance that at least 0.2mm falls at your location — not how long it rains. For Phnom Penh we combine the hourly probability curve, expected volume in millimetres, and the city's own rainfall record into a single umbrella verdict.
| Factor | Weight | What it measures |
|---|---|---|
| Hourly probability | 40% | Peak and sustained chance of measurable rain across the next 24 hours. |
| Expected volume | 30% | Total millimetres, which separates a passing shower from a genuine soaking. |
| Timing & duration | 20% | When rain starts, when it eases, and the longest continuous dry window. |
| Local rain type | 10% | Drizzle, brief showers, thunderstorms or monsoon — each needs different gear. |
Live hourly values come from Open-Meteo and refresh through the day. Monthly rainfall figures are climate normals, so they describe a typical year rather than a forecast.
Phnom Penh records rain on roughly 96 days a year — about a 26% chance on any given day — totalling around 900mm.
September, with about 129mm over 14 rain days. That is 14% of the entire year's rainfall in a single month.
January is the driest month at 21mm across roughly 2 days.
With rain on about 26% of days and steady rain as the dominant type, a compact umbrella or waterproof shell is worth packing for Phnom Penh outside January.
No. Probability is the chance that at least 0.2mm of rain falls at your location at some point in the period. Check the expected millimetres alongside it: 40% with 0.4mm is a passing shower, 40% with 12mm is a soaking.