July is one of the warmer months of the year in Sarnia, with average highs near 25.7°C and lows around 16.4°C (mean 21°C). It is about average for rainfall, averaging 77 mm of rainfall and 75% relative humidity across the period.
July is one of the warmer months of the year in Sarnia. Across 45 years of records, the warmest July in Sarnia was 2020 — when the month averaged 23.5°C — while the coldest was 1992 at 18.1°C. Typical July days reach 25.7°C with nights near 16.4°C. The long-term trend is warming, about 0.5°C per decade.
July is about average for rainfall in Sarnia, averaging 77 mm of rainfall. The wettest July on record was 1992 with 153 mm, while the driest was 2001 at 18 mm.
Relative humidity in Sarnia during July averages 75%. The most humid Julys were 1986 and 2013 at 80%, and the least humid was 1988 at 65%.
July receives about 6.1 kWh/m²/day of solar energy in Sarnia. The sunniest Julys were 2002 and 2020 at 6.6 kWh/m²/day, and the cloudiest were 2000, 2004 and 2013, among others at 5.6.
Average wind speed in Sarnia during July is 2.6 m/s. The windiest July was 2006 at 3.1 m/s, while the calmest was 1989 at 2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 20.5°C | 20.4°C | 20.9°C | 21.7°C | 22.2°C | +1.7°C |
| Avg High | 25.4°C | 25.2°C | 25.6°C | 26.1°C | 26.8°C | +1.4°C |
| Avg Low | 15.6°C | 15.7°C | 16.2°C | 17.2°C | 17.7°C | +2.1°C |
| Avg Rain | 74 mm | 76 mm | 73 mm | 80 mm | 81 mm | +7 mm |
July temperatures in Sarnia have risen by about 2.2°C between 1981–1985 and 2021–2025.
July has ranged from a record low of 7.2°C (1983) to a record high of 34.7°C (1988).
Rainfall in July is about average for rainfall, averaging 77 mm, with a wettest year of 153 mm.
One of the best times to visit Sarnia
July is one of the best times to visit Sarnia. Expect days averaging 25.7°C and nights around 16.4°C (mean 21°C) — warmer than Sarnia's yearly average — with moderate rainfall (77 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 | 27.6°C | 22.9°C | 18.3°C | 32.7°C | 12.6°C | 65 mm | 73% | 2.4 m/s | 6.1 |
| 2024 | 26.1°C | 21.8°C | 17.6°C | 29.6°C | 10.9°C | 103 mm | 76% | 2.3 m/s | 6 |
| 2023 | 26.1°C | 21.7°C | 17.4°C | 30.4°C | 14.5°C | 117 mm | 74% | 2.4 m/s | 5.8 |
| 2022 | 26.8°C | 21.9°C | 17.0°C | 30.8°C | 12.6°C | 47 mm | 70% | 2.8 m/s | 6.3 |
| 2021 | 26.0°C | 21.6°C | 17.1°C | 31.0°C | 12.7°C | 83 mm | 74% | 3 m/s | 5.7 |
| 2020 🔥 | 28.0°C | 23.5°C | 19.1°C | 31.3°C | 16.3°C | 72 mm | 75% | 2.5 m/s | 6.6 |
| 2019 | 26.7°C | 22.1°C | 17.5°C | 30.9°C | 13.5°C | 51 mm | 80% | 2.6 m/s | 6.5 |
| 2018 | 26.1°C | 21.7°C | 17.3°C | 31.7°C | 12.5°C | 67 mm | 76% | 2.4 m/s | 6.4 |
| 2017 | 25.5°C | 21.2°C | 16.8°C | 28.3°C | 13.2°C | 70 mm | 79% | 2.6 m/s | 6.1 |
| 2016 | 26.5°C | 22.2°C | 17.9°C | 30.7°C | 11.4°C | 87 mm | 77% | 2.7 m/s | 6.2 |
| 2015 | 25.2°C | 20.3°C | 15.4°C | 30.1°C | 8.9°C | 65 mm | 75% | 2.3 m/s | 6.3 |
| 2014 | 23.4°C | 19.1°C | 14.7°C | 28.6°C | 10.6°C | 95 mm | 77% | 2.8 m/s | 6 |
| 2013 | 25.3°C | 21.3°C | 17.2°C | 31.2°C | 11.3°C | 100 mm | 80% | 2.5 m/s | 5.6 |
| 2012 | 27.4°C | 23.1°C | 18.7°C | 33.0°C | 15.0°C | 101 mm | 73% | 2.5 m/s | 6.4 |
| 2011 | 27.4°C | 23.0°C | 18.5°C | 32.3°C | 13.4°C | 74 mm | 78% | 2.4 m/s | 6.5 |
| 2010 | 27.4°C | 22.9°C | 18.4°C | 32.1°C | 11.2°C | 90 mm | 74% | 2.7 m/s | 6.4 |
| 2009 | 23.1°C | 18.7°C | 14.4°C | 26.0°C | 11.2°C | 66 mm | 78% | 2.6 m/s | 5.7 |
| 2008 | 25.7°C | 21.3°C | 16.8°C | 29.0°C | 10.6°C | 96 mm | 76% | 2.9 m/s | 6.5 |
| 2007 | 25.7°C | 20.8°C | 15.8°C | 32.0°C | 11.1°C | 36 mm | 69% | 2.7 m/s | 6.2 |
| 2006 | 27.4°C | 22.8°C | 18.1°C | 31.8°C | 12.9°C | 90 mm | 75% | 3.1 m/s | 6 |
| 2005 | 27.8°C | 22.9°C | 18.0°C | 32.4°C | 13.2°C | 86 mm | 71% | 2.4 m/s | 6.4 |
| 2004 | 24.3°C | 19.9°C | 15.4°C | 29.3°C | 12.1°C | 96 mm | 78% | 2.9 m/s | 5.6 |
| 2003 | 25.9°C | 20.9°C | 16.0°C | 30.5°C | 12.1°C | 52 mm | 70% | 2.9 m/s | 6 |
| 2002 | 26.9°C | 22.0°C | 17.1°C | 30.8°C | 11.1°C | 74 mm | 72% | 2.7 m/s | 6.6 |
| 2001 | 25.7°C | 20.5°C | 15.2°C | 30.8°C | 8.7°C | 18 mm | 69% | 2.7 m/s | 6.5 |
| 2000 | 23.9°C | 19.6°C | 15.4°C | 27.7°C | 11.9°C | 117 mm | 76% | 2.7 m/s | 5.6 |
| 1999 | 28.0°C | 23.0°C | 17.9°C | 31.9°C | 13.2°C | 86 mm | 73% | 2.9 m/s | 6.2 |
| 1998 | 26.3°C | 21.5°C | 16.7°C | 31.4°C | 12.8°C | 63 mm | 69% | 2.9 m/s | 6.3 |
| 1997 | 25.2°C | 20.3°C | 15.3°C | 30.5°C | 10.2°C | 70 mm | 76% | 2.8 m/s | 6.2 |
| 1996 | 23.5°C | 18.7°C | 13.9°C | 27.3°C | 9.3°C | 67 mm | 75% | 2.7 m/s | 6.2 |
| 1995 | 25.7°C | 21.0°C | 16.4°C | 31.1°C | 10.3°C | 64 mm | 78% | 2.8 m/s | 5.8 |
| 1994 | 24.7°C | 20.2°C | 15.8°C | 28.5°C | 10.2°C | 95 mm | 79% | 2.6 m/s | 5.9 |
| 1993 | 25.5°C | 21.0°C | 16.6°C | 29.0°C | 11.4°C | 49 mm | 77% | 2.8 m/s | 5.8 |
| 1992 ❄️ 🌧️ | 22.9°C | 18.1°C | 13.4°C | 26.6°C | 8.8°C | 153 mm | 78% | 2.9 m/s | 6 |
| 1991 | 25.5°C | 20.7°C | 15.9°C | 30.6°C | 11.7°C | 53 mm | 73% | 2.5 m/s | 6.4 |
| 1990 | 24.4°C | 19.7°C | 14.9°C | 30.3°C | 9.9°C | 58 mm | 74% | 2.8 m/s | 5.8 |
| 1989 | 25.8°C | 21.1°C | 16.5°C | 30.1°C | 12.1°C | 69 mm | 74% | 2 m/s | 6 |
| 1988 | 28.5°C | 22.8°C | 17.1°C | 34.7°C | 10.0°C | 88 mm | 65% | 2.3 m/s | 6.2 |
| 1987 | 26.4°C | 21.6°C | 16.9°C | 30.5°C | 10.1°C | 84 mm | 76% | 2.5 m/s | 6.3 |
| 1986 | 24.5°C | 19.8°C | 15.1°C | 29.4°C | 8.3°C | 74 mm | 80% | 2.7 m/s | 6.4 |
| 1985 | 23.4°C | 18.9°C | 14.4°C | 26.7°C | 10.0°C | 79 mm | 76% | 2.8 m/s | 6.4 |
| 1984 | 24.0°C | 18.9°C | 13.9°C | 28.9°C | 8.7°C | 60 mm | 74% | 2.6 m/s | 5.6 |
| 1983 | 25.4°C | 20.6°C | 15.8°C | 29.3°C | 7.2°C | 87 mm | 79% | 2.6 m/s | — |
| 1982 | 25.0°C | 19.7°C | 14.5°C | 28.0°C | 8.6°C | 61 mm | 76% | 2.6 m/s | — |
| 1981 | 25.8°C | 20.9°C | 16.1°C | 30.2°C | 11.2°C | 69 mm | 72% | 2.4 m/s | — |
Actual recorded July data for each year, 1981–2025 — sourced from NASA POWER.
The average high in July is around 25.7°C with lows near 16.4°C (mean 21°C), based on 45 years of NASA POWER data.
July averages 77 mm of rainfall in Sarnia, about average for rainfall. The wettest on record was 153 mm in 1992.
The hottest July reached 34.7°C in 1988. The coldest dipped to 7.2°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average July temperatures have risen by about 2.2°C. Daytime highs moved from 24.7°C to 26.5°C and overnight lows from 14.9°C to 17.5°C over the same span.
July is one of the warmer months of the year in Sarnia and about average for rainfall, so plan for around 25.7°C daytime highs and 16.4°C at night.
Not quite — July is the 12th coolest month in Sarnia, averaging 21°C.
For July in Sarnia, pack light layers you can adjust through the day, with typical highs of 25.7°C and lows of 16.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in July averages 75% — moderately humid.
Average wind speed in July is 2.6 m/s. The windiest July on record averaged 3.1 m/s (2006).
The wettest July on record was 1992 with 153 mm. On average, July sees 77 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 July, 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 July specifically, along with year-by-year records and how the month has changed over the decades.
