September is one of the warmer months of the year in Gravenhurst, with average highs near 21.5°C and lows around 10.3°C (mean 15.9°C). It is a relatively wet time of year, averaging 62 mm of rainfall and 71% relative humidity across the period.
September is one of the warmer months of the year in Gravenhurst. Across 45 years of records, the warmest Septembers in Gravenhurst were 2015 and 2024 — when the month averaged 19.4°C — while the coldest was 1993 at 12.5°C. Typical September days reach 21.5°C with nights near 10.3°C. The long-term trend is warming, about 1°C per decade.
September is a relatively wet time of year in Gravenhurst, averaging 62 mm of rainfall. The wettest September on record was 1984 with 143 mm, while the driest was 2025 at 12 mm.
Relative humidity in Gravenhurst during September averages 71%. The most humid September was 1981 at 81%, and the least humid was 2025 at 62%.
September receives about 4 kWh/m²/day of solar energy in Gravenhurst. The sunniest Septembers were 2004 and 2009 at 4.6 kWh/m²/day, and the cloudiest were 1993 and 2006 at 3.2.
Average wind speed in Gravenhurst during September is 0.5 m/s. The windiest Septembers were 2021, 2022 and 2024, among others at 0.5 m/s, while the calmest were 2015, 2023 and 2025, among others at 0.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.5°C | 14.7°C | 16.3°C | 17.0°C | 17.6°C | +3.1°C |
| Avg High | 19.9°C | 20.2°C | 21.9°C | 22.7°C | 23.6°C | +3.7°C |
| Avg Low | 9.1°C | 9.2°C | 10.7°C | 11.4°C | 11.7°C | +2.6°C |
| Avg Rain | 93 mm | 79 mm | 56 mm | 44 mm | 27 mm | -66 mm |
September temperatures in Gravenhurst have risen by about 3.8°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -2.4°C (1981) to a record high of 33.3°C (1999).
Rainfall in September is a relatively wet time of year, averaging 62 mm, with a wettest year of 143 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 1.1°C per decade while lows rose 0.8°C per decade, widening the gap between day and night.
One of the best times to visit Gravenhurst
September is one of the best times to visit Gravenhurst. Expect days averaging 21.5°C and nights around 10.3°C (mean 15.9°C) — warmer than Gravenhurst's yearly average — with moderate rainfall (62 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 | 24.3°C | 18.1°C | 11.8°C | 29.6°C | 6.6°C | 12 mm | 62% | 0.4 m/s | 4.5 |
| 2024 | 25.9°C | 19.4°C | 13.0°C | 30.7°C | 7.2°C | 44 mm | 66% | 0.5 m/s | 4.3 |
| 2023 | 24.6°C | 18.5°C | 12.4°C | 33.0°C | 6.6°C | 12 mm | 65% | 0.4 m/s | 4.5 |
| 2022 | 22.6°C | 16.9°C | 11.2°C | 29.9°C | 2.1°C | 25 mm | 69% | 0.5 m/s | 3.9 |
| 2021 | 22.5°C | 16.9°C | 11.4°C | 27.3°C | 5.7°C | 50 mm | 69% | 0.5 m/s | 4.1 |
| 2020 | 21.4°C | 16.0°C | 10.5°C | 27.6°C | 3.4°C | 21 mm | 69% | 0.5 m/s | 4 |
| 2019 | 21.9°C | 16.5°C | 11.0°C | 27.5°C | 5.2°C | 60 mm | 74% | 0.5 m/s | 3.6 |
| 2018 | 24.0°C | 18.3°C | 12.6°C | 32.5°C | 6.0°C | 23 mm | 68% | 0.5 m/s | 3.9 |
| 2017 | 24.2°C | 18.3°C | 12.3°C | 32.8°C | 4.5°C | 47 mm | 70% | 0.5 m/s | 4.3 |
| 2016 | 24.3°C | 18.4°C | 12.6°C | 32.0°C | 5.0°C | 36 mm | 65% | 0.5 m/s | 4.3 |
| 2015 🔥 | 25.4°C | 19.4°C | 13.4°C | 31.8°C | 7.1°C | 27 mm | 67% | 0.4 m/s | 4.2 |
| 2014 | 21.5°C | 15.7°C | 9.9°C | 28.8°C | 1.3°C | 48 mm | 73% | 0.5 m/s | 4 |
| 2013 | 21.4°C | 15.6°C | 9.8°C | 30.6°C | 2.2°C | 55 mm | 69% | 0.5 m/s | 4.1 |
| 2012 | 21.1°C | 15.8°C | 10.5°C | 29.8°C | 4.1°C | 51 mm | 68% | 0.5 m/s | 4 |
| 2011 | 22.8°C | 17.1°C | 11.4°C | 31.2°C | 2.4°C | 39 mm | 69% | 0.5 m/s | 3.7 |
| 2010 | 20.3°C | 15.3°C | 10.4°C | 32.8°C | 4.9°C | 52 mm | 74% | 0.5 m/s | 3.3 |
| 2009 | 22.6°C | 16.5°C | 10.4°C | 27.9°C | 1.7°C | 20 mm | 67% | 0.5 m/s | 4.6 |
| 2008 | 22.6°C | 16.7°C | 10.7°C | 31.9°C | 5.4°C | 40 mm | 69% | 0.4 m/s | 3.9 |
| 2007 | 22.8°C | 16.9°C | 11.0°C | 32.1°C | 5.3°C | 44 mm | 68% | 0.4 m/s | 4.4 |
| 2006 | 19.9°C | 14.5°C | 9.2°C | 26.6°C | 3.4°C | 68 mm | 74% | 0.5 m/s | 3.2 |
| 2005 | 24.1°C | 18.1°C | 12.1°C | 30.6°C | 6.0°C | 47 mm | 68% | 0.5 m/s | 4.4 |
| 2004 | 22.9°C | 17.0°C | 11.1°C | 28.3°C | 3.4°C | 27 mm | 73% | 0.5 m/s | 4.6 |
| 2003 | 21.2°C | 16.0°C | 10.9°C | 30.7°C | 4.2°C | 98 mm | 72% | 0.5 m/s | 3.9 |
| 2002 | 23.7°C | 18.2°C | 12.8°C | 32.3°C | 7.5°C | 40 mm | 70% | 0.5 m/s | 4.3 |
| 2001 | 19.8°C | 14.8°C | 9.9°C | 28.4°C | 4.0°C | 87 mm | 76% | 0.4 m/s | 3.9 |
| 2000 | 19.5°C | 14.1°C | 8.7°C | 28.8°C | -1.8°C | 94 mm | 74% | 0.5 m/s | 3.9 |
| 1999 | 22.5°C | 16.9°C | 11.2°C | 33.3°C | 2.8°C | 89 mm | 70% | 0.5 m/s | 4 |
| 1998 | 21.9°C | 16.4°C | 11.0°C | 27.8°C | 3.2°C | 60 mm | 71% | 0.5 m/s | 4.3 |
| 1997 | 20.1°C | 14.7°C | 9.3°C | 25.4°C | 1.1°C | 65 mm | 73% | 0.5 m/s | 3.9 |
| 1996 | 20.9°C | 15.8°C | 10.6°C | 31.2°C | 3.6°C | 101 mm | 75% | 0.4 m/s | 3.4 |
| 1995 | 19.4°C | 13.3°C | 7.3°C | 26.0°C | 1.9°C | 50 mm | 69% | 0.4 m/s | 4 |
| 1994 | 20.8°C | 15.1°C | 9.4°C | 28.6°C | 2.5°C | 32 mm | 74% | 0.4 m/s | 3.9 |
| 1993 ❄️ | 17.5°C | 12.5°C | 7.5°C | 27.9°C | -0.1°C | 128 mm | 75% | 0.5 m/s | 3.2 |
| 1992 | 19.4°C | 13.9°C | 8.4°C | 25.2°C | -0.4°C | 117 mm | 75% | 0.4 m/s | 3.8 |
| 1991 | 19.6°C | 14.1°C | 8.6°C | 29.0°C | -1.4°C | 58 mm | 69% | 0.5 m/s | 3.8 |
| 1990 | 20.0°C | 14.4°C | 8.8°C | 28.1°C | 1.2°C | 89 mm | 73% | 0.4 m/s | 3.4 |
| 1989 | 21.3°C | 15.3°C | 9.4°C | 28.0°C | -2.0°C | 77 mm | 70% | 0.4 m/s | 3.9 |
| 1988 | 20.6°C | 14.8°C | 9.1°C | 28.4°C | 3.2°C | 63 mm | 69% | 0.4 m/s | 4.2 |
| 1987 | 21.4°C | 16.0°C | 10.6°C | 27.9°C | 3.5°C | 26 mm | 70% | 0.4 m/s | 3.5 |
| 1986 | 19.2°C | 13.8°C | 8.4°C | 26.6°C | 0.8°C | 98 mm | 76% | 0.4 m/s | 3.5 |
| 1985 | 20.5°C | 15.0°C | 9.5°C | 26.7°C | 3.1°C | 108 mm | 78% | 0.4 m/s | 4.1 |
| 1984 🌧️ | 18.0°C | 12.9°C | 7.7°C | 26.8°C | 1.6°C | 143 mm | 76% | 0.4 m/s | 3.7 |
| 1983 | 21.4°C | 15.8°C | 10.1°C | 30.2°C | 4.6°C | 87 mm | 72% | 0.4 m/s | — |
| 1982 | 19.3°C | 13.9°C | 8.4°C | 29.2°C | 4.1°C | 109 mm | 77% | 0.4 m/s | — |
| 1981 | 17.7°C | 13.3°C | 8.8°C | 26.7°C | -2.4°C | 128 mm | 81% | 0.4 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 21.5°C with lows near 10.3°C (mean 15.9°C), based on 45 years of NASA POWER data.
September averages 62 mm of rainfall in Gravenhurst, a relatively wet time of year. The wettest on record was 143 mm in 1984.
The hottest September reached 33.3°C in 1999. The coldest dipped to -2.4°C in 1981.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 3.8°C. Daytime highs moved from 19.4°C to 24°C and overnight lows from 8.9°C to 12°C over the same span.
September is one of the warmer months of the year in Gravenhurst and a relatively wet time of year, so plan for around 21.5°C daytime highs and 10.3°C at night.
Not quite — September is the 9th coolest month in Gravenhurst, averaging 15.9°C.
For September in Gravenhurst, pack light layers you can adjust through the day, with typical highs of 21.5°C and lows of 10.3°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 71% — moderately humid.
Average wind speed in September is 0.5 m/s. The windiest September on record averaged 0.5 m/s (1991).
The wettest September on record was 1984 with 143 mm. On average, September sees 62 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 Gravenhurst behaves each September, 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 September specifically, along with year-by-year records and how the month has changed over the decades.
