Ottawa records about 919mm of rain across roughly 113 wet days a year, which is a 31% chance on an average day. August is the wettest month at 89mm (10% of the annual total) and February the driest at 44mm. Local rain type: snow mix. Ottawa gets heavy snow in winter and humid thunderstorms in summer. The world's largest skating rink (Rideau Canal) only forms in the coldest winters.
Chance of rain on an average day: 31%
Rainfall climatology for Ottawa. 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 | 919mm |
| Rain days per year | 113 |
| Odds on an average day | 31% |
| Wettest month | August — 89mm over 12 days |
| Driest month | February — 44mm over 6 days |
| Rain type | snow mix |
| Best dry window | September offers crisp, dry conditions with spectacular fall foliage. |
| Worst rain window | December through March buries the city in snow — sometimes over 2 meters total. |
August delivers 102% more rain than February (89mm vs 44mm). That gap is the difference between planning around showers and ignoring them.
No single month holds more than 10% of the annual total, so rain in Ottawa is spread through the year — there is no season you can rely on being dry.
Ottawa rain typically comes as discrete showers, so a compact umbrella and a flexible plan are usually enough.
Rain falls on about 12 days in August against 6 in February — 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 | 8 | 27% | -5°C |
| February | 44mm | 6 | 20% | -5°C |
| March | 56mm | 7 | 23% | -1°C |
| April | 69mm | 9 | 30% | 6°C |
| May | 80mm | 10 | 33% | 15°C |
| June | 85mm | 11 | 37% | 22°C |
| July | 83mm | 11 | 37% | 26°C |
| August | 89mm | 12 | 40% | 26°C |
| September | 82mm | 11 | 37% | 22°C |
| October | 79mm | 10 | 33% | 15°C |
| November | 78mm | 10 | 33% | 6°C |
| December | 64mm | 8 | 27% | -1°C |
Rain probability is the chance that at least 0.2mm falls at your location — not how long it rains. For Ottawa 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.
Ottawa records rain on roughly 113 days a year — about a 31% chance on any given day — totalling around 919mm.
August, with about 89mm over 12 rain days. That is 10% of the entire year's rainfall in a single month.
February is the driest month at 44mm across roughly 6 days. September offers crisp, dry conditions with spectacular fall foliage.
Ottawa gets heavy snow in winter and humid thunderstorms in summer. The world's largest skating rink (Rideau Canal) only forms in the coldest winters.
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.