September is one of the warmer months of the year in Mississauga, with average highs near 20°C and lows around 13.8°C (mean 16.9°C). It is about average for rainfall, averaging 66 mm of rainfall and 75% relative humidity across the period.
September is one of the warmer months of the year in Mississauga. Across 45 years of records, the warmest September in Mississauga was 2016 — when the month averaged 20.7°C — while the coldest was 1993 at 12.5°C. Typical September days reach 20°C with nights near 13.8°C. The long-term trend is warming, about 1.6°C per decade.
September is about average for rainfall in Mississauga, averaging 66 mm of rainfall. The wettest September on record was 1986 with 154 mm, while the driest was 2023 at 18 mm.
Relative humidity in Mississauga during September averages 75%. The most humid September was 1986 at 82%, and the least humid was 1998 at 69%.
September receives about 4.1 kWh/m²/day of solar energy in Mississauga. The sunniest September was 2005 at 4.7 kWh/m²/day, and the cloudiest were 1993 and 2006 at 3.2.
Average wind speed in Mississauga during September is 3.5 m/s. The windiest September was 2000 at 4.4 m/s, while the calmest were 1987, 2017 and 2025, among others at 2.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.5°C | 14.9°C | 17.6°C | 18.9°C | 19.5°C | +5°C |
| Avg High | 17.9°C | 18.2°C | 20.6°C | 21.8°C | 22.4°C | +4.5°C |
| Avg Low | 11.1°C | 11.5°C | 14.6°C | 16.2°C | 16.6°C | +5.5°C |
| Avg Rain | 81 mm | 59 mm | 71 mm | 66 mm | 45 mm | -36 mm |
September temperatures in Mississauga have risen by about 4.7°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 1.6°C (1993) to a record high of 30.9°C (2017).
Rainfall in September is about average for rainfall, averaging 66 mm, with a wettest year of 154 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 1.4°C per decade while lows rose 1.8°C per decade, narrowing the gap between day and night.
One of the best times to visit Mississauga
September is one of the best times to visit Mississauga. Expect days averaging 20°C and nights around 13.8°C (mean 16.9°C) — warmer than Mississauga's yearly average — with moderate rainfall (66 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 | 22.5°C | 19.5°C | 16.5°C | 26.2°C | 12.4°C | 41 mm | 70% | 2.8 m/s | 4.5 |
| 2024 | 23.0°C | 20.3°C | 17.5°C | 25.6°C | 12.7°C | 52 mm | 76% | 3.3 m/s | 4.3 |
| 2023 | 22.6°C | 19.7°C | 16.8°C | 29.5°C | 13.4°C | 18 mm | 71% | 3.3 m/s | 4.4 |
| 2022 | 22.1°C | 19.3°C | 16.5°C | 27.7°C | 9.9°C | 35 mm | 70% | 3.7 m/s | 3.9 |
| 2021 | 22.9°C | 19.9°C | 16.9°C | 25.9°C | 12.4°C | 92 mm | 70% | 4.3 m/s | 4.3 |
| 2020 | 21.1°C | 18.3°C | 15.5°C | 26.1°C | 10.5°C | 33 mm | 71% | 4.1 m/s | 4.2 |
| 2019 | 21.9°C | 19.1°C | 16.3°C | 26.6°C | 13.7°C | 61 mm | 76% | 3.7 m/s | 3.8 |
| 2018 | 22.9°C | 20.3°C | 17.8°C | 29.4°C | 12.6°C | 64 mm | 75% | 3.8 m/s | 3.9 |
| 2017 | 22.9°C | 19.7°C | 16.6°C | 30.9°C | 10.8°C | 41 mm | 72% | 2.8 m/s | 4.6 |
| 2016 🔥 | 23.5°C | 20.7°C | 18.0°C | 28.8°C | 13.7°C | 52 mm | 70% | 3.8 m/s | 4.4 |
| 2015 | 23.2°C | 20.4°C | 17.7°C | 29.0°C | 12.6°C | 77 mm | 75% | 3.5 m/s | 4.2 |
| 2014 | 20.7°C | 17.8°C | 14.9°C | 26.6°C | 10.1°C | 69 mm | 75% | 3.4 m/s | 4.1 |
| 2013 | 20.4°C | 17.4°C | 14.5°C | 27.6°C | 9.5°C | 63 mm | 74% | 3.6 m/s | 4.1 |
| 2012 | 21.0°C | 18.2°C | 15.4°C | 27.6°C | 10.1°C | 83 mm | 71% | 3.8 m/s | 4.2 |
| 2011 | 21.2°C | 18.6°C | 16.0°C | 27.9°C | 10.8°C | 80 mm | 77% | 3.7 m/s | 3.8 |
| 2010 | 20.1°C | 17.2°C | 14.3°C | 28.4°C | 10.5°C | 69 mm | 75% | 4.2 m/s | 3.6 |
| 2009 | 21.1°C | 18.5°C | 15.9°C | 24.8°C | 9.0°C | 43 mm | 73% | 3.7 m/s | 4.4 |
| 2008 | 21.1°C | 18.4°C | 15.7°C | 28.5°C | 12.2°C | 74 mm | 75% | 3.4 m/s | 4 |
| 2007 | 22.3°C | 19.1°C | 15.9°C | 28.1°C | 10.9°C | 45 mm | 71% | 3.6 m/s | 4.5 |
| 2006 | 19.9°C | 17.4°C | 14.8°C | 24.9°C | 8.3°C | 102 mm | 76% | 4.3 m/s | 3.2 |
| 2005 | 23.6°C | 20.3°C | 17.0°C | 28.3°C | 11.5°C | 84 mm | 72% | 4.2 m/s | 4.7 |
| 2004 | 22.6°C | 19.6°C | 16.6°C | 25.9°C | 12.1°C | 53 mm | 73% | 3.6 m/s | 4.6 |
| 2003 | 17.4°C | 14.4°C | 11.3°C | 23.9°C | 5.0°C | 82 mm | 80% | 3.4 m/s | 4.1 |
| 2002 | 20.5°C | 16.8°C | 13.1°C | 27.5°C | 9.5°C | 64 mm | 75% | 3 m/s | 4.6 |
| 2001 | 17.6°C | 14.1°C | 10.7°C | 23.7°C | 4.8°C | 72 mm | 76% | 3.1 m/s | 4.3 |
| 2000 | 20.2°C | 17.4°C | 14.5°C | 27.8°C | 6.1°C | 89 mm | 73% | 4.4 m/s | 4 |
| 1999 | 20.7°C | 17.2°C | 13.8°C | 25.7°C | 6.3°C | 94 mm | 72% | 3.4 m/s | 4.2 |
| 1998 | 22.8°C | 19.6°C | 16.3°C | 28.3°C | 11.3°C | 40 mm | 69% | 3.7 m/s | 4.3 |
| 1997 | 20.4°C | 17.3°C | 14.1°C | 24.5°C | 9.0°C | 55 mm | 73% | 4.2 m/s | 3.9 |
| 1996 | 17.7°C | 14.6°C | 11.6°C | 24.3°C | 6.0°C | 76 mm | 81% | 3.2 m/s | 3.4 |
| 1995 | 16.7°C | 13.0°C | 9.3°C | 24.4°C | 4.7°C | 36 mm | 73% | 3 m/s | 4.1 |
| 1994 | 17.3°C | 13.8°C | 10.2°C | 21.2°C | 5.9°C | 44 mm | 78% | 3 m/s | 3.9 |
| 1993 ❄️ | 15.6°C | 12.5°C | 9.4°C | 21.5°C | 1.6°C | 61 mm | 77% | 3.4 m/s | 3.2 |
| 1992 | 16.3°C | 13.1°C | 9.9°C | 20.8°C | 3.5°C | 80 mm | 81% | 3.5 m/s | 4.1 |
| 1991 | 17.2°C | 13.8°C | 10.4°C | 23.2°C | 3.8°C | 44 mm | 70% | 3.1 m/s | 4.2 |
| 1990 | 17.2°C | 13.8°C | 10.4°C | 23.8°C | 4.3°C | 59 mm | 79% | 3.3 m/s | 3.6 |
| 1989 | 17.6°C | 14.0°C | 10.4°C | 23.3°C | 2.7°C | 71 mm | 78% | 3 m/s | 4 |
| 1988 | 17.3°C | 13.6°C | 10.0°C | 21.3°C | 7.1°C | 60 mm | 76% | 3.5 m/s | 4.3 |
| 1987 | 17.6°C | 14.1°C | 10.7°C | 22.5°C | 6.7°C | 69 mm | 81% | 2.8 m/s | 3.7 |
| 1986 🌧️ | 17.0°C | 13.8°C | 10.6°C | 22.0°C | 5.4°C | 154 mm | 82% | 3.2 m/s | 3.6 |
| 1985 | 19.6°C | 16.2°C | 12.9°C | 25.5°C | 6.7°C | 41 mm | 76% | 3.3 m/s | 4.5 |
| 1984 | 17.1°C | 13.8°C | 10.5°C | 22.3°C | 5.2°C | 83 mm | 76% | 3.2 m/s | 4 |
| 1983 | 19.6°C | 16.0°C | 12.4°C | 26.1°C | 7.0°C | 47 mm | 73% | 3.6 m/s | — |
| 1982 | 17.5°C | 14.1°C | 10.7°C | 25.0°C | 5.8°C | 84 mm | 79% | 2.8 m/s | — |
| 1981 | 17.6°C | 14.8°C | 12.1°C | 24.0°C | 5.7°C | 122 mm | 81% | 3.6 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 20°C with lows near 13.8°C (mean 16.9°C), based on 45 years of NASA POWER data.
September averages 66 mm of rainfall in Mississauga, about average for rainfall. The wettest on record was 154 mm in 1986.
The hottest September reached 30.9°C in 2017. The coldest dipped to 1.6°C in 1993.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 4.7°C. Daytime highs moved from 18.3°C to 22.6°C and overnight lows from 11.7°C to 16.8°C over the same span.
September is one of the warmer months of the year in Mississauga and about average for rainfall, so plan for around 20°C daytime highs and 13.8°C at night.
Not quite — September is the 10th coolest month in Mississauga, averaging 16.9°C.
For September in Mississauga, pack light layers you can adjust through the day, with typical highs of 20°C and lows of 13.8°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 75% — moderately humid.
Average wind speed in September is 3.5 m/s. The windiest September on record averaged 4.4 m/s (2000).
The wettest September on record was 1986 with 154 mm. On average, September sees 66 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 Mississauga 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.
