August is one of the warmer months of the year in Ottawa, with average highs near 24.7°C and lows around 13.9°C (mean 19.3°C). It is about average for rainfall, averaging 90 mm of rainfall and 78% relative humidity across the period.
August is one of the warmer months of the year in Ottawa. Across 45 years of records, the warmest August in Ottawa was 2021 — when the month averaged 22.8°C — while the coldest was 1982 at 16.2°C. Typical August days reach 24.7°C with nights near 13.9°C. The long-term trend is warming, about 0.5°C per decade.
August is about average for rainfall in Ottawa, averaging 90 mm of rainfall. The wettest August on record was 2022 with 154 mm, while the driest was 2002 at 37 mm.
Relative humidity in Ottawa during August averages 78%. The most humid August was 2000 at 82%, and the least humid was 2025 at 66%.
August receives about 5.1 kWh/m²/day of solar energy in Ottawa. The sunniest Augusts were 1996 and 2002 at 5.6 kWh/m²/day, and the cloudiest was 1988 at 4.3.
Average wind speed in Ottawa during August is 0.3 m/s. The windiest Augusts were 2023, 2024 and 2025, among others at 0.3 m/s, while the calmest were 2023, 2024 and 2025, among others at 0.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 18.2°C | 18.9°C | 19.5°C | 19.8°C | 20.3°C | +2.1°C |
| Avg High | 23.6°C | 24.5°C | 24.9°C | 25.2°C | 25.8°C | +2.2°C |
| Avg Low | 12.8°C | 13.4°C | 14.1°C | 14.4°C | 14.9°C | +2.1°C |
| Avg Rain | 100 mm | 79 mm | 83 mm | 89 mm | 102 mm | +2 mm |
August temperatures in Ottawa have risen by about 2.3°C between 1981–1985 and 2021–2025.
August has ranged from a record low of 2.9°C (1982) to a record high of 35.3°C (2025).
Rainfall in August is about average for rainfall, averaging 90 mm, with a wettest year of 154 mm.
One of the best times to visit Ottawa
August is one of the best times to visit Ottawa. Expect days averaging 24.7°C and nights around 13.9°C (mean 19.3°C) — warmer than Ottawa's yearly average — with higher rainfall (90 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 26.8°C | 20.4°C | 14.0°C | 35.3°C | 8.9°C | 53 mm | 66% | 0.3 m/s | 5.3 |
| 2024 | 25.6°C | 20.2°C | 14.9°C | 34.4°C | 9.6°C | 123 mm | 79% | 0.3 m/s | 4.5 |
| 2023 | 24.0°C | 18.6°C | 13.2°C | 28.4°C | 7.5°C | 98 mm | 78% | 0.3 m/s | 4.8 |
| 2022 🌧️ | 25.8°C | 20.4°C | 15.1°C | 32.5°C | 10.2°C | 154 mm | 78% | 0.3 m/s | 5 |
| 2021 🔥 | 28.4°C | 22.8°C | 17.3°C | 33.8°C | 11.5°C | 47 mm | 74% | 0.3 m/s | 5 |
| 2020 | 24.3°C | 19.5°C | 14.8°C | 29.7°C | 8.5°C | 140 mm | 79% | 0.3 m/s | 5.2 |
| 2019 | 24.3°C | 18.9°C | 13.4°C | 28.1°C | 10.1°C | 60 mm | 78% | 0.3 m/s | 5.4 |
| 2018 | 26.1°C | 21.2°C | 16.2°C | 31.2°C | 10.3°C | 77 mm | 81% | 0.3 m/s | 4.9 |
| 2017 | 23.3°C | 18.4°C | 13.5°C | 27.2°C | 7.6°C | 85 mm | 81% | 0.3 m/s | 5.3 |
| 2016 | 27.6°C | 21.8°C | 16.1°C | 34.3°C | 10.7°C | 97 mm | 74% | 0.3 m/s | 5.2 |
| 2015 | 25.7°C | 20.2°C | 14.6°C | 31.3°C | 11.2°C | 91 mm | 76% | 0.3 m/s | 4.9 |
| 2014 | 23.8°C | 18.6°C | 13.4°C | 29.0°C | 8.4°C | 93 mm | 79% | 0.3 m/s | 5.1 |
| 2013 | 24.8°C | 19.2°C | 13.5°C | 30.2°C | 8.2°C | 82 mm | 77% | 0.3 m/s | 5.1 |
| 2012 | 26.7°C | 20.9°C | 15.2°C | 33.8°C | 9.1°C | 73 mm | 71% | 0.3 m/s | 5 |
| 2011 | 24.6°C | 19.5°C | 14.4°C | 29.2°C | 10.4°C | 101 mm | 81% | 0.3 m/s | 5 |
| 2010 | 25.1°C | 19.6°C | 14.1°C | 32.3°C | 8.2°C | 133 mm | 79% | 0.3 m/s | 5.1 |
| 2009 | 24.2°C | 19.3°C | 14.5°C | 30.6°C | 6.6°C | 91 mm | 81% | 0.3 m/s | 5 |
| 2008 | 23.6°C | 18.6°C | 13.6°C | 27.4°C | 8.2°C | 78 mm | 81% | 0.3 m/s | 5.1 |
| 2007 | 24.7°C | 18.9°C | 13.1°C | 31.8°C | 7.1°C | 92 mm | 78% | 0.3 m/s | 5.4 |
| 2006 | 24.1°C | 18.7°C | 13.3°C | 33.1°C | 7.1°C | 82 mm | 76% | 0.3 m/s | 5.5 |
| 2005 | 26.3°C | 20.8°C | 15.2°C | 31.4°C | 9.2°C | 95 mm | 75% | 0.3 m/s | 5.1 |
| 2004 | 23.1°C | 17.9°C | 12.8°C | 28.8°C | 6.5°C | 88 mm | 81% | 0.3 m/s | 4.7 |
| 2003 | 26.4°C | 21.1°C | 15.8°C | 31.2°C | 8.5°C | 89 mm | 77% | 0.3 m/s | 4.9 |
| 2002 | 26.0°C | 20.3°C | 14.7°C | 34.3°C | 9.8°C | 37 mm | 76% | 0.3 m/s | 5.6 |
| 2001 | 27.0°C | 20.9°C | 14.8°C | 34.0°C | 8.9°C | 77 mm | 73% | 0.3 m/s | 5.2 |
| 2000 | 23.6°C | 18.5°C | 13.5°C | 27.4°C | 8.2°C | 102 mm | 82% | 0.3 m/s | 4.7 |
| 1999 | 24.3°C | 18.8°C | 13.4°C | 31.1°C | 9.6°C | 53 mm | 73% | 0.3 m/s | 5 |
| 1998 | 25.0°C | 19.7°C | 14.5°C | 30.2°C | 8.2°C | 64 mm | 78% | 0.3 m/s | 5 |
| 1997 | 23.4°C | 17.9°C | 12.4°C | 29.4°C | 7.8°C | 79 mm | 76% | 0.3 m/s | 5 |
| 1996 | 24.7°C | 19.0°C | 13.2°C | 28.9°C | 7.9°C | 47 mm | 79% | 0.3 m/s | 5.6 |
| 1995 | 25.7°C | 19.7°C | 13.8°C | 31.4°C | 8.5°C | 72 mm | 74% | 0.3 m/s | 5.4 |
| 1994 | 23.0°C | 17.5°C | 12.0°C | 27.1°C | 6.9°C | 97 mm | 80% | 0.3 m/s | 5.2 |
| 1993 | 25.1°C | 19.7°C | 14.3°C | 29.5°C | 8.7°C | 69 mm | 81% | 0.3 m/s | 5.2 |
| 1992 | 22.9°C | 17.6°C | 12.3°C | 28.4°C | 7.6°C | 111 mm | 81% | 0.3 m/s | 4.7 |
| 1991 | 25.6°C | 20.0°C | 14.4°C | 31.0°C | 8.8°C | 87 mm | 77% | 0.3 m/s | 5 |
| 1990 | 24.9°C | 19.4°C | 14.0°C | 30.0°C | 8.5°C | 111 mm | 80% | 0.3 m/s | 5.2 |
| 1989 | 23.7°C | 18.2°C | 12.6°C | 30.8°C | 5.2°C | 87 mm | 77% | 0.3 m/s | 5.2 |
| 1988 | 24.6°C | 19.6°C | 14.6°C | 31.4°C | 7.4°C | 129 mm | 80% | 0.3 m/s | 4.3 |
| 1987 | 23.5°C | 17.8°C | 12.1°C | 30.3°C | 7.0°C | 54 mm | 75% | 0.3 m/s | 5 |
| 1986 | 22.2°C | 17.0°C | 11.8°C | 33.0°C | 4.8°C | 126 mm | 81% | 0.3 m/s | 4.8 |
| 1985 | 22.9°C | 17.6°C | 12.2°C | 28.4°C | 6.7°C | 75 mm | 78% | 0.3 m/s | 4.8 |
| 1984 | 24.8°C | 19.7°C | 14.5°C | 30.9°C | 6.1°C | 148 mm | 81% | 0.3 m/s | 5.1 |
| 1983 | 25.0°C | 19.5°C | 13.9°C | 28.6°C | 6.8°C | 65 mm | 78% | 0.3 m/s | — |
| 1982 ❄️ | 21.9°C | 16.2°C | 10.5°C | 27.5°C | 2.9°C | 88 mm | 77% | 0.3 m/s | — |
| 1981 | 23.4°C | 18.2°C | 13.0°C | 28.3°C | 7.3°C | 131 mm | 82% | 0.3 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 24.7°C with lows near 13.9°C (mean 19.3°C), based on 45 years of NASA POWER data.
August averages 90 mm of rainfall in Ottawa, about average for rainfall. The wettest on record was 154 mm in 2022.
The hottest August reached 35.3°C in 2025. The coldest dipped to 2.9°C in 1982.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have risen by about 2.3°C. Daytime highs moved from 23.6°C to 26.1°C and overnight lows from 12.8°C to 14.9°C over the same span.
August is one of the warmer months of the year in Ottawa and about average for rainfall, so plan for around 24.7°C daytime highs and 13.9°C at night.
Not quite — August is the 11th coolest month in Ottawa, averaging 19.3°C.
For August in Ottawa, pack light layers you can adjust through the day, with typical highs of 24.7°C and lows of 13.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in August averages 78% — quite humid.
Average wind speed in August is 0.3 m/s. The windiest August on record averaged 0.3 m/s (1981).
The wettest August on record was 2022 with 154 mm. On average, August sees 90 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Ottawa behaves each August, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for August specifically, along with year-by-year records and how the month has changed over the decades.
