Sri Lanka records about 2400mm of rain across roughly 160 wet days a year, which is a 44% chance on an average day. May is the wettest month at 370mm (15% of the annual total) and January the driest at 60mm. Local rain type: monsoon. Sri Lanka's dual monsoon means there's always a dry coast — when the southwest coast is wet (May-September), the east coast is dry, and vice versa. Always pack a compact umbrella regardless of season.
Chance of rain on an average day: 44%
Rainfall climatology for Sri Lanka. 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 | 2400mm |
| Rain days per year | 160 |
| Odds on an average day | 44% |
| Wettest month | May — 370mm over 25 days |
| Driest month | January — 60mm over 4 days |
| Rain type | monsoon |
| Best dry window | January through March is dry on the west and south coasts — Galle, Unawatuna, and hill country are at their best. |
| Worst rain window | May brings the heaviest southwest monsoon rain — Colombo and the south coast can receive flooding rains. |
May delivers 517% more rain than January (370mm vs 60mm). That gap is the difference between planning around showers and ignoring them.
No single month holds more than 15% of the annual total, so rain in Sri Lanka is spread through the year — there is no season you can rely on being dry.
Sri Lanka rain arrives in short, heavy bursts — shelter and timing matter more than gear.
Rain falls on about 25 days in May against 4 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 | 60mm | 4 | 13% | 30°C |
| February | 70mm | 5 | 17% | 30°C |
| March | 130mm | 9 | 30% | 30°C |
| April | 250mm | 17 | 57% | 31°C |
| May | 370mm | 25 | 83% | 31°C |
| June | 180mm | 12 | 40% | 32°C |
| July | 130mm | 9 | 30% | 32°C |
| August | 110mm | 7 | 23% | 32°C |
| September | 230mm | 16 | 53% | 32°C |
| October | 350mm | 24 | 80% | 31°C |
| November | 310mm | 21 | 70% | 31°C |
| December | 170mm | 12 | 40% | 30°C |
Rain probability is the chance that at least 0.2mm falls at your location — not how long it rains. For Sri Lanka 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.
Sri Lanka records rain on roughly 160 days a year — about a 44% chance on any given day — totalling around 2400mm.
May, with about 370mm over 25 rain days. That is 15% of the entire year's rainfall in a single month.
January is the driest month at 60mm across roughly 4 days. January through March is dry on the west and south coasts — Galle, Unawatuna, and hill country are at their best.
Sri Lanka's dual monsoon means there's always a dry coast — when the southwest coast is wet (May-September), the east coast is dry, and vice versa. Always pack a compact umbrella regardless of season.
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.