August is one of the warmer months of the year in Sarnia, with average highs near 25.1°C and lows around 16.1°C (mean 20.6°C). It is a relatively wet time of year, averaging 81 mm of rainfall and 75% relative humidity across the period.
August is one of the warmer months of the year in Sarnia. Across 45 years of records, the warmest August in Sarnia was 2021 — when the month averaged 23.7°C — while the coldest was 1992 at 17°C. Typical August days reach 25.1°C with nights near 16.1°C. The long-term trend is warming, about 0.6°C per decade.
August is a relatively wet time of year in Sarnia, averaging 81 mm of rainfall. The wettest August on record was 1985 with 153 mm, while the driest was 2010 at 28 mm.
Relative humidity in Sarnia during August averages 75%. The most humid August was 2018 at 81%, and the least humid was 2025 at 68%.
August receives about 5.3 kWh/m²/day of solar energy in Sarnia. The sunniest Augusts were 2008 and 2019 at 5.8 kWh/m²/day, and the cloudiest was 1997 at 4.4.
Average wind speed in Sarnia during August is 2.6 m/s. The windiest August was 1999 at 3.1 m/s, while the calmest was 1996 at 2.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 19.4°C | 20.0°C | 21.0°C | 21.2°C | 21.8°C | +2.4°C |
| Avg High | 24.2°C | 24.6°C | 25.5°C | 25.5°C | 26.2°C | +2°C |
| Avg Low | 14.6°C | 15.4°C | 16.6°C | 16.9°C | 17.3°C | +2.7°C |
| Avg Rain | 97 mm | 73 mm | 67 mm | 82 mm | 93 mm | -4 mm |
August temperatures in Sarnia have risen by about 2.5°C between 1981–1985 and 2021–2025.
August has ranged from a record low of 5°C (1982) to a record high of 34.5°C (2001).
Rainfall in August is a relatively wet time of year, averaging 81 mm, with a wettest year of 153 mm.
One of the best times to visit Sarnia
August is one of the best times to visit Sarnia. Expect days averaging 25.1°C and nights around 16.1°C (mean 20.6°C) — warmer than Sarnia's yearly average — with higher rainfall (81 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 | 26.2°C | 21.4°C | 16.6°C | 32.1°C | 10.4°C | 45 mm | 68% | 2.6 m/s | 5.5 |
| 2024 | 25.9°C | 21.5°C | 17.1°C | 30.9°C | 11.5°C | 89 mm | 73% | 2.6 m/s | 5.2 |
| 2023 | 24.4°C | 19.9°C | 15.5°C | 28.8°C | 11.1°C | 150 mm | 77% | 2.9 m/s | 5 |
| 2022 | 26.5°C | 22.0°C | 17.5°C | 31.8°C | 13.9°C | 92 mm | 74% | 2.6 m/s | 5.4 |
| 2021 🔥 | 28.2°C | 23.7°C | 19.2°C | 31.1°C | 14.3°C | 65 mm | 73% | 2.4 m/s | 5.5 |
| 2020 | 26.2°C | 22.0°C | 17.7°C | 29.7°C | 13.9°C | 117 mm | 76% | 2.7 m/s | 5.6 |
| 2019 | 25.2°C | 21.0°C | 16.7°C | 28.1°C | 12.9°C | 55 mm | 75% | 2.8 m/s | 5.8 |
| 2018 | 26.3°C | 22.4°C | 18.5°C | 30.1°C | 13.0°C | 114 mm | 81% | 2.6 m/s | 5.1 |
| 2017 | 23.9°C | 19.7°C | 15.5°C | 28.1°C | 12.1°C | 82 mm | 78% | 2.6 m/s | 5.2 |
| 2016 | 27.1°C | 22.9°C | 18.7°C | 31.0°C | 14.2°C | 112 mm | 78% | 2.6 m/s | 5.6 |
| 2015 | 24.5°C | 20.2°C | 15.9°C | 29.3°C | 11.5°C | 90 mm | 77% | 2.7 m/s | 5.4 |
| 2014 | 24.4°C | 20.0°C | 15.5°C | 28.1°C | 10.0°C | 109 mm | 80% | 2.5 m/s | 5.2 |
| 2013 | 24.5°C | 20.2°C | 15.8°C | 29.0°C | 11.2°C | 57 mm | 78% | 2.6 m/s | 5.2 |
| 2012 | 25.4°C | 21.0°C | 16.6°C | 30.9°C | 11.8°C | 91 mm | 73% | 2.5 m/s | 5.7 |
| 2011 | 25.3°C | 21.1°C | 16.9°C | 28.5°C | 13.3°C | 83 mm | 77% | 2.7 m/s | 5.5 |
| 2010 | 28.0°C | 23.2°C | 18.4°C | 31.8°C | 13.0°C | 28 mm | 71% | 2.7 m/s | 5.2 |
| 2009 | 24.3°C | 20.2°C | 16.1°C | 29.7°C | 11.3°C | 96 mm | 78% | 3 m/s | 5.2 |
| 2008 | 25.2°C | 20.5°C | 15.8°C | 29.7°C | 11.3°C | 52 mm | 73% | 2.8 m/s | 5.8 |
| 2007 | 25.8°C | 21.6°C | 17.4°C | 33.3°C | 12.1°C | 123 mm | 76% | 2.6 m/s | 5.1 |
| 2006 | 25.9°C | 21.5°C | 17.1°C | 33.6°C | 11.8°C | 74 mm | 72% | 2.7 m/s | 5.3 |
| 2005 | 27.4°C | 22.7°C | 18.0°C | 32.0°C | 13.0°C | 47 mm | 71% | 2.8 m/s | 5.2 |
| 2004 | 23.2°C | 19.1°C | 15.1°C | 27.5°C | 10.3°C | 65 mm | 77% | 3 m/s | 5.1 |
| 2003 | 26.1°C | 21.5°C | 16.9°C | 31.2°C | 12.6°C | 42 mm | 73% | 2.6 m/s | 5.4 |
| 2002 | 26.1°C | 21.3°C | 16.5°C | 30.2°C | 13.1°C | 31 mm | 72% | 2.7 m/s | 5.6 |
| 2001 | 26.6°C | 21.8°C | 17.0°C | 34.5°C | 13.2°C | 65 mm | 71% | 2.8 m/s | 5.3 |
| 2000 | 24.5°C | 20.2°C | 15.9°C | 28.7°C | 11.1°C | 70 mm | 77% | 2.8 m/s | 5.2 |
| 1999 | 24.5°C | 20.1°C | 15.6°C | 29.6°C | 11.2°C | 59 mm | 71% | 3.1 m/s | 5 |
| 1998 | 26.2°C | 21.8°C | 17.4°C | 30.7°C | 11.6°C | 90 mm | 73% | 2.3 m/s | 5.4 |
| 1997 | 23.1°C | 18.9°C | 14.8°C | 28.3°C | 11.8°C | 84 mm | 78% | 2.9 m/s | 4.4 |
| 1996 | 25.5°C | 20.4°C | 15.3°C | 29.8°C | 11.6°C | 31 mm | 75% | 2.2 m/s | 5.5 |
| 1995 | 27.1°C | 22.4°C | 17.7°C | 30.6°C | 13.0°C | 74 mm | 76% | 2.5 m/s | 5 |
| 1994 | 23.1°C | 18.5°C | 14.0°C | 27.0°C | 9.8°C | 76 mm | 78% | 2.6 m/s | 5.1 |
| 1993 | 25.2°C | 20.7°C | 16.2°C | 29.4°C | 10.8°C | 78 mm | 78% | 2.3 m/s | 5.2 |
| 1992 ❄️ | 21.7°C | 17.0°C | 12.3°C | 27.5°C | 7.4°C | 96 mm | 80% | 2.9 m/s | 5.6 |
| 1991 | 25.2°C | 20.4°C | 15.6°C | 31.1°C | 12.4°C | 66 mm | 74% | 2.6 m/s | 5.4 |
| 1990 | 24.6°C | 19.9°C | 15.2°C | 28.6°C | 11.4°C | 81 mm | 77% | 2.3 m/s | 4.8 |
| 1989 | 24.5°C | 19.8°C | 15.1°C | 28.7°C | 9.0°C | 68 mm | 75% | 2.7 m/s | 5.3 |
| 1988 | 27.1°C | 22.0°C | 16.9°C | 33.6°C | 9.1°C | 63 mm | 69% | 2.9 m/s | 5.4 |
| 1987 | 24.0°C | 19.4°C | 14.8°C | 29.6°C | 7.7°C | 115 mm | 75% | 2.9 m/s | 4.8 |
| 1986 | 22.4°C | 17.6°C | 12.9°C | 27.7°C | 5.0°C | 89 mm | 76% | 2.5 m/s | 5.1 |
| 1985 🌧️ | 22.7°C | 18.0°C | 13.3°C | 27.1°C | 9.0°C | 153 mm | 79% | 2.3 m/s | 5 |
| 1984 | 25.0°C | 20.2°C | 15.3°C | 27.9°C | 9.9°C | 114 mm | 77% | 2.5 m/s | 5.4 |
| 1983 | 25.3°C | 20.3°C | 15.2°C | 29.3°C | 9.4°C | 75 mm | 78% | 2.3 m/s | — |
| 1982 | 22.6°C | 17.5°C | 12.4°C | 27.7°C | 5.0°C | 78 mm | 75% | 2.5 m/s | — |
| 1981 | 24.5°C | 19.9°C | 15.4°C | 28.3°C | 10.5°C | 120 mm | 76% | 2.5 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 25.1°C with lows near 16.1°C (mean 20.6°C), based on 45 years of NASA POWER data.
August averages 81 mm of rainfall in Sarnia, a relatively wet time of year. The wettest on record was 153 mm in 1985.
The hottest August reached 34.5°C in 2001. The coldest dipped to 5°C in 1982.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have risen by about 2.5°C. Daytime highs moved from 24°C to 26.2°C and overnight lows from 14.3°C to 17.2°C over the same span.
August is one of the warmer months of the year in Sarnia and a relatively wet time of year, so plan for around 25.1°C daytime highs and 16.1°C at night.
Not quite — August is the 11th coolest month in Sarnia, averaging 20.6°C.
For August in Sarnia, pack light layers you can adjust through the day, with typical highs of 25.1°C and lows of 16.1°C. Bring an umbrella or light rain jacket too.
Relative humidity in August averages 75% — quite humid.
Average wind speed in August is 2.6 m/s. The windiest August on record averaged 3.1 m/s (1999).
The wettest August on record was 1985 with 153 mm. On average, August sees 81 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 Sarnia 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.
