September is one of the warmer months of the year in Innisfil, with average highs near 21.2°C and lows around 11.6°C (mean 16.4°C). It is a relatively wet time of year, averaging 60 mm of rainfall and 72% relative humidity across the period.
September is one of the warmer months of the year in Innisfil. Across 45 years of records, the warmest September in Innisfil was 2015 — when the month averaged 19.9°C — while the coldest was 1993 at 13.1°C. Typical September days reach 21.2°C with nights near 11.6°C. The long-term trend is warming, about 1°C per decade.
September is a relatively wet time of year in Innisfil, averaging 60 mm of rainfall. The wettest September on record was 1993 with 118 mm, while the driest was 2023 at 14 mm.
Relative humidity in Innisfil during September averages 72%. The most humid September was 1981 at 81%, and the least humid was 2025 at 64%.
September receives about 4 kWh/m²/day of solar energy in Innisfil. 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 Innisfil during September is 1.4 m/s. The windiest Septembers were 2010 and 2021 at 1.7 m/s, while the calmest were 1982, 2017 and 2025 at 1.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.9°C | 15.1°C | 16.8°C | 17.6°C | 18.2°C | +3.3°C |
| Avg High | 19.6°C | 19.8°C | 21.6°C | 22.4°C | 23.1°C | +3.5°C |
| Avg Low | 10.1°C | 10.4°C | 12.0°C | 12.9°C | 13.3°C | +3.2°C |
| Avg Rain | 77 mm | 73 mm | 55 mm | 52 mm | 36 mm | -40 mm |
September temperatures in Innisfil have risen by about 3.8°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -0.1°C (1989) to a record high of 33.1°C (2002).
Rainfall in September is a relatively wet time of year, averaging 60 mm, with a wettest year of 118 mm.
One of the best times to visit Innisfil
September is one of the best times to visit Innisfil. Expect days averaging 21.2°C and nights around 11.6°C (mean 16.4°C) — warmer than Innisfil's yearly average — with moderate rainfall (60 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 | 23.8°C | 18.6°C | 13.4°C | 28.1°C | 9.1°C | 28 mm | 64% | 1.2 m/s | 4.5 |
| 2024 | 24.7°C | 19.5°C | 14.3°C | 29.1°C | 7.9°C | 52 mm | 69% | 1.4 m/s | 4.3 |
| 2023 | 24.0°C | 18.8°C | 13.7°C | 32.5°C | 9.3°C | 14 mm | 67% | 1.3 m/s | 4.5 |
| 2022 | 22.2°C | 17.6°C | 13.0°C | 30.1°C | 5.6°C | 28 mm | 69% | 1.5 m/s | 3.9 |
| 2021 | 22.4°C | 17.8°C | 13.2°C | 26.4°C | 7.6°C | 69 mm | 70% | 1.7 m/s | 4.1 |
| 2020 | 21.5°C | 16.9°C | 12.3°C | 27.3°C | 5.4°C | 28 mm | 69% | 1.6 m/s | 4 |
| 2019 | 22.1°C | 17.5°C | 12.9°C | 27.2°C | 8.2°C | 51 mm | 74% | 1.5 m/s | 3.6 |
| 2018 | 23.4°C | 18.7°C | 14.1°C | 31.8°C | 7.8°C | 32 mm | 71% | 1.6 m/s | 3.9 |
| 2017 | 23.8°C | 18.7°C | 13.6°C | 32.2°C | 6.4°C | 43 mm | 71% | 1.2 m/s | 4.3 |
| 2016 | 24.1°C | 19.1°C | 14.2°C | 30.7°C | 7.5°C | 46 mm | 66% | 1.5 m/s | 4.3 |
| 2015 🔥 | 24.9°C | 19.9°C | 15.0°C | 31.1°C | 8.3°C | 47 mm | 69% | 1.4 m/s | 4.2 |
| 2014 | 21.3°C | 16.4°C | 11.5°C | 28.3°C | 4.8°C | 62 mm | 74% | 1.5 m/s | 4 |
| 2013 | 21.0°C | 16.1°C | 11.3°C | 31.2°C | 4.6°C | 62 mm | 72% | 1.5 m/s | 4.1 |
| 2012 | 20.8°C | 16.4°C | 11.9°C | 28.5°C | 6.0°C | 61 mm | 69% | 1.5 m/s | 4 |
| 2011 | 21.8°C | 17.3°C | 12.8°C | 29.3°C | 5.1°C | 55 mm | 72% | 1.4 m/s | 3.7 |
| 2010 | 20.3°C | 16.1°C | 12.0°C | 31.7°C | 7.2°C | 66 mm | 74% | 1.7 m/s | 3.3 |
| 2009 | 21.7°C | 16.8°C | 11.8°C | 27.0°C | 3.9°C | 35 mm | 70% | 1.4 m/s | 4.6 |
| 2008 | 21.9°C | 17.0°C | 12.1°C | 31.0°C | 7.6°C | 53 mm | 72% | 1.3 m/s | 3.9 |
| 2007 | 22.3°C | 17.3°C | 12.3°C | 31.2°C | 6.2°C | 59 mm | 70% | 1.4 m/s | 4.4 |
| 2006 | 19.7°C | 15.2°C | 10.7°C | 25.6°C | 3.9°C | 77 mm | 75% | 1.5 m/s | 3.2 |
| 2005 | 23.9°C | 18.8°C | 13.6°C | 29.8°C | 8.1°C | 43 mm | 68% | 1.6 m/s | 4.4 |
| 2004 | 23.1°C | 17.9°C | 12.7°C | 28.6°C | 5.8°C | 29 mm | 72% | 1.4 m/s | 4.6 |
| 2003 | 20.5°C | 16.0°C | 11.4°C | 28.3°C | 5.4°C | 68 mm | 72% | 1.4 m/s | 3.9 |
| 2002 | 23.6°C | 18.7°C | 13.8°C | 33.1°C | 8.8°C | 37 mm | 69% | 1.4 m/s | 4.3 |
| 2001 | 19.7°C | 15.2°C | 10.7°C | 27.4°C | 3.5°C | 71 mm | 74% | 1.4 m/s | 3.9 |
| 2000 | 19.8°C | 15.2°C | 10.5°C | 29.8°C | 1.0°C | 78 mm | 73% | 1.6 m/s | 3.9 |
| 1999 | 22.3°C | 17.3°C | 12.4°C | 31.2°C | 4.4°C | 72 mm | 69% | 1.4 m/s | 4 |
| 1998 | 21.8°C | 17.1°C | 12.4°C | 27.1°C | 5.5°C | 60 mm | 71% | 1.5 m/s | 4.3 |
| 1997 | 20.1°C | 15.4°C | 10.8°C | 25.0°C | 3.9°C | 56 mm | 73% | 1.6 m/s | 3.9 |
| 1996 | 20.1°C | 15.7°C | 11.4°C | 28.6°C | 4.8°C | 96 mm | 76% | 1.3 m/s | 3.4 |
| 1995 | 18.8°C | 13.6°C | 8.5°C | 26.0°C | 4.0°C | 55 mm | 70% | 1.3 m/s | 4 |
| 1994 | 20.4°C | 15.4°C | 10.4°C | 27.6°C | 6.4°C | 31 mm | 73% | 1.3 m/s | 3.9 |
| 1993 ❄️ 🌧️ | 17.4°C | 13.1°C | 8.7°C | 27.1°C | 0.6°C | 118 mm | 75% | 1.5 m/s | 3.2 |
| 1992 | 18.7°C | 14.1°C | 9.5°C | 24.8°C | 1.7°C | 108 mm | 77% | 1.5 m/s | 3.8 |
| 1991 | 19.2°C | 14.4°C | 9.7°C | 27.8°C | 0.9°C | 52 mm | 68% | 1.4 m/s | 3.8 |
| 1990 | 19.6°C | 14.7°C | 9.9°C | 27.5°C | 3.3°C | 84 mm | 74% | 1.4 m/s | 3.4 |
| 1989 | 20.5°C | 15.5°C | 10.6°C | 27.1°C | -0.1°C | 79 mm | 71% | 1.3 m/s | 3.9 |
| 1988 | 20.4°C | 15.3°C | 10.2°C | 27.5°C | 5.1°C | 47 mm | 69% | 1.6 m/s | 4.2 |
| 1987 | 20.5°C | 15.8°C | 11.0°C | 27.5°C | 5.1°C | 37 mm | 73% | 1.3 m/s | 3.5 |
| 1986 | 18.6°C | 14.0°C | 9.4°C | 26.0°C | 3.1°C | 96 mm | 77% | 1.3 m/s | 3.5 |
| 1985 | 20.4°C | 15.5°C | 10.6°C | 27.1°C | 4.2°C | 77 mm | 76% | 1.3 m/s | 4.1 |
| 1984 | 18.1°C | 13.4°C | 8.7°C | 25.6°C | 3.0°C | 98 mm | 75% | 1.4 m/s | 3.7 |
| 1983 | 21.4°C | 16.3°C | 11.1°C | 29.3°C | 6.5°C | 60 mm | 69% | 1.3 m/s | — |
| 1982 | 19.4°C | 14.4°C | 9.4°C | 28.4°C | 4.6°C | 86 mm | 75% | 1.2 m/s | — |
| 1981 | 17.5°C | 13.9°C | 10.2°C | 25.8°C | 0.4°C | 111 mm | 81% | 1.5 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 21.2°C with lows near 11.6°C (mean 16.4°C), based on 45 years of NASA POWER data.
September averages 60 mm of rainfall in Innisfil, a relatively wet time of year. The wettest on record was 118 mm in 1993.
The hottest September reached 33.1°C in 2002. The coldest dipped to -0.1°C in 1989.
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 23.4°C and overnight lows from 10°C to 13.5°C over the same span.
September is one of the warmer months of the year in Innisfil and a relatively wet time of year, so plan for around 21.2°C daytime highs and 11.6°C at night.
Not quite — September is the 9th coolest month in Innisfil, averaging 16.4°C.
For September in Innisfil, pack light layers you can adjust through the day, with typical highs of 21.2°C and lows of 11.6°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 72% — moderately humid.
Average wind speed in September is 1.4 m/s. The windiest September on record averaged 1.7 m/s (2010).
The wettest September on record was 1993 with 118 mm. On average, September sees 60 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 Innisfil 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.
