Climate averages 1991–2020
Ottawa weather
in August.
A warm, wet month: the 2nd warmest and the joint 7th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
August is a warm month in Ottawa: daytime highs average 24.6°C and nights cool to about 16.0°C. By daytime temperature it is the 2nd warmest of the 12 months.
Expect about 90 mm of rain on roughly 11 days, which makes August a wet month (the joint 7th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 14 h 06 min on an average August day.
The nearest other city in this atlas is Gatineau (7 km away). In August its highs average 24.5°C, about as warm as Ottawa, with 90 mm of rain.
Among the 86 cities listed in Canada, Ottawa ranks joint 26th of 86 for the warmest August highs and joint 64th of 86 for the driest August (rainfall, lowest first). The mean August high of those 86 cities is 23.8°C; Ottawa is 0.8°C warmer than that mean.
From August to September, average highs fall by 4.2°C to 20.4°C, and monthly rainfall rises from 90 mm to 95 mm.
The annual picture
August in context
Monthly precipitation
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Ottawa climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | -5.0°C-14.2°C | -14.2°C | 73 | 10.5 | 9.29 h |
| February | -3.3°C-12.9°C | -12.9°C | 58 | 8.8 | 10.410 h |
| March | 2.5°C-7.0°C | -7.0°C | 73 | 9.9 | 11.912 h |
| April | 10.7°C0.6°C | 0.6°C | 90 | 11.1 | 13.513 h |
| May | 18.6°C7.9°C | 7.9°C | 88 | 11.2 | 14.915 h |
| June | 23.4°C13.5°C | 13.5°C | 99 | 11.6 | 15.616 h |
| July | 25.8°C16.5°C | 16.5°C | 98 | 12.4 | 15.315 h |
| August, selected | 24.6°C16.0°C | 16.0°C | 90 | 11.1 | 14.114 h |
| September | 20.4°C12.0°C | 12.0°C | 95 | 10.3 | 12.613 h |
| October | 12.8°C5.6°C | 5.6°C | 99 | 12.2 | 11.011 h |
| November | 5.5°C-0.8°C | -0.8°C | 83 | 11.4 | 9.610 h |
| December | -1.1°C-7.9°C | -7.9°C | 79 | 11.5 | 8.89 h |
Precipitation (rain or snow, as water) is the average of the 30 separate monthly totals. A wet day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
August in nearby cities
- Gatineau in AugustCanada · 7 kmHigh 24.5°C · Low 16.1°C · 90 mm rain
- Gloucester, Canada in AugustCanada · 8 kmHigh 24.5°C · Low 15.7°C · 86 mm rain
- Nepean in AugustCanada · 9 kmHigh 24.5°C · Low 15.7°C · 86 mm rain
- Orléans, Canada in AugustCanada · 16 kmHigh 24.3°C · Low 15.6°C · 93 mm rain
- Kanata in AugustCanada · 21 kmHigh 24.5°C · Low 15.7°C · 84 mm rain
- Pierrefonds-Roxboro in AugustCanada · 145 kmHigh 24.5°C · Low 16.7°C · 91 mm rain
- Kingston, Canada in AugustCanada · 145 kmHigh 24.1°C · Low 18.7°C · 96 mm rain
- Saint-Louis-de-Terrebonne in AugustCanada · 152 kmHigh 24.2°C · Low 16.0°C · 96 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Ottawa) is explained once on the Ottawa year overview and on the Sources, method and limits page.
Gatineau lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.