September is one of the warmer months of the year in Guelph, with average highs near 23.2°C and lows around 11.1°C (mean 17.2°C). It is a relatively wet time of year, averaging 70 mm of rainfall and 71% relative humidity across the period.
September is one of the warmer months of the year in Guelph. Across 45 years of records, the warmest September in Guelph was 2002 — when the month averaged 20.1°C — while the coldest was 1993 at 14.2°C. Typical September days reach 23.2°C with nights near 11.1°C. The long-term trend is warming, about 0.7°C per decade.
September is a relatively wet time of year in Guelph, averaging 70 mm of rainfall. The wettest September on record was 1986 with 176 mm, while the driest was 2023 at 20 mm.
Relative humidity in Guelph during September averages 71%. The most humid September was 1986 at 78%, and the least humid was 1991 at 63%.
September receives about 4.1 kWh/m²/day of solar energy in Guelph. The sunniest Septembers were 2004 and 2005 at 4.7 kWh/m²/day, and the cloudiest were 1993 and 2006 at 3.2.
Average wind speed in Guelph during September is 2.6 m/s. The windiest September was 2010 at 3.1 m/s, while the calmest were 2017 and 2025 at 2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.2°C | 16.2°C | 17.5°C | 17.8°C | 18.5°C | +2.3°C |
| Avg High | 22.2°C | 22.3°C | 23.7°C | 23.7°C | 24.6°C | +2.4°C |
| Avg Low | 10.3°C | 10.0°C | 11.4°C | 12.0°C | 12.4°C | +2.1°C |
| Avg Rain | 80 mm | 67 mm | 71 mm | 75 mm | 54 mm | -27 mm |
September temperatures in Guelph have risen by about 2.6°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -1°C (1993) to a record high of 35.5°C (2002).
Rainfall in September is a relatively wet time of year, averaging 70 mm, with a wettest year of 176 mm.
One of the best times to visit Guelph
September is one of the best times to visit Guelph. Expect days averaging 23.2°C and nights around 11.1°C (mean 17.2°C) — warmer than Guelph's yearly average — with moderate rainfall (70 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 | 25.3°C | 18.9°C | 12.6°C | 29.3°C | 6.7°C | 52 mm | 65% | 2 m/s | 4.6 |
| 2024 | 25.9°C | 19.8°C | 13.7°C | 30.0°C | 8.0°C | 36 mm | 69% | 2.2 m/s | 4.4 |
| 2023 | 24.8°C | 18.7°C | 12.6°C | 34.4°C | 6.9°C | 20 mm | 69% | 2.2 m/s | 4.2 |
| 2022 | 24.2°C | 18.1°C | 12.0°C | 32.9°C | 3.8°C | 32 mm | 67% | 2.4 m/s | 4 |
| 2021 | 23.7°C | 17.9°C | 12.1°C | 28.4°C | 6.1°C | 131 mm | 72% | 2.8 m/s | 4.3 |
| 2020 | 23.6°C | 17.4°C | 11.2°C | 29.8°C | 2.9°C | 50 mm | 69% | 2.9 m/s | 4.2 |
| 2019 | 24.4°C | 18.4°C | 12.4°C | 30.5°C | 8.1°C | 53 mm | 74% | 2.7 m/s | 3.8 |
| 2018 | 24.2°C | 19.0°C | 13.8°C | 33.3°C | 6.9°C | 64 mm | 75% | 2.6 m/s | 3.9 |
| 2017 | 25.2°C | 18.9°C | 12.6°C | 33.4°C | 5.1°C | 38 mm | 70% | 2 m/s | 4.6 |
| 2016 | 25.2°C | 19.4°C | 13.6°C | 32.4°C | 7.3°C | 62 mm | 69% | 2.5 m/s | 4.5 |
| 2015 | 25.6°C | 19.7°C | 13.8°C | 33.5°C | 7.5°C | 66 mm | 71% | 2.4 m/s | 4.3 |
| 2014 | 22.3°C | 16.5°C | 10.8°C | 29.8°C | 4.8°C | 113 mm | 75% | 2.4 m/s | 4.2 |
| 2013 | 22.4°C | 16.1°C | 9.9°C | 33.5°C | 3.2°C | 84 mm | 73% | 2.4 m/s | 4.2 |
| 2012 | 22.1°C | 16.2°C | 10.4°C | 31.2°C | 4.2°C | 94 mm | 70% | 2.4 m/s | 4.2 |
| 2011 | 23.0°C | 17.6°C | 12.2°C | 33.1°C | 5.0°C | 86 mm | 75% | 2.6 m/s | 3.7 |
| 2010 | 22.3°C | 16.5°C | 10.7°C | 33.3°C | 5.6°C | 87 mm | 72% | 3.1 m/s | 3.6 |
| 2009 | 23.1°C | 17.2°C | 11.4°C | 28.2°C | 3.1°C | 38 mm | 71% | 2.3 m/s | 4.4 |
| 2008 | 23.0°C | 17.2°C | 11.4°C | 32.3°C | 5.8°C | 92 mm | 75% | 2.2 m/s | 4.1 |
| 2007 | 25.8°C | 18.9°C | 12.0°C | 34.5°C | 3.4°C | 37 mm | 65% | 2.6 m/s | 4.5 |
| 2006 | 21.1°C | 15.7°C | 10.4°C | 27.8°C | 2.9°C | 84 mm | 75% | 2.9 m/s | 3.2 |
| 2005 | 25.8°C | 19.1°C | 12.4°C | 32.3°C | 4.7°C | 60 mm | 68% | 2.8 m/s | 4.7 |
| 2004 | 25.1°C | 18.7°C | 12.2°C | 30.1°C | 6.0°C | 40 mm | 69% | 2.4 m/s | 4.7 |
| 2003 | 22.3°C | 16.6°C | 10.8°C | 29.1°C | 3.3°C | 95 mm | 72% | 2.8 m/s | 4.2 |
| 2002 🔥 | 26.7°C | 20.1°C | 13.5°C | 35.5°C | 7.1°C | 63 mm | 64% | 2.5 m/s | 4.6 |
| 2001 | 22.4°C | 16.4°C | 10.4°C | 30.8°C | 2.8°C | 84 mm | 69% | 2.7 m/s | 4.2 |
| 2000 | 21.3°C | 15.5°C | 9.7°C | 31.6°C | 0.4°C | 113 mm | 75% | 2.8 m/s | 3.9 |
| 1999 | 24.8°C | 18.1°C | 11.3°C | 32.7°C | 2.2°C | 74 mm | 64% | 2.6 m/s | 4.4 |
| 1998 | 25.5°C | 18.8°C | 12.1°C | 32.9°C | 5.2°C | 38 mm | 64% | 2.6 m/s | 4.4 |
| 1997 | 22.4°C | 16.3°C | 10.1°C | 28.5°C | 2.9°C | 53 mm | 71% | 2.9 m/s | 4 |
| 1996 | 22.1°C | 16.7°C | 11.3°C | 30.5°C | 3.1°C | 109 mm | 73% | 2.6 m/s | 3.4 |
| 1995 | 21.5°C | 15.1°C | 8.6°C | 30.5°C | 3.1°C | 32 mm | 65% | 2.6 m/s | 4.3 |
| 1994 | 22.7°C | 16.3°C | 9.9°C | 30.2°C | 4.5°C | 41 mm | 71% | 2.6 m/s | 4 |
| 1993 ❄️ | 19.7°C | 14.2°C | 8.6°C | 29.6°C | -1.0°C | 86 mm | 71% | 2.9 m/s | 3.2 |
| 1992 | 20.5°C | 14.8°C | 9.0°C | 26.8°C | 0.9°C | 118 mm | 78% | 2.9 m/s | 3.8 |
| 1991 | 22.1°C | 15.7°C | 9.4°C | 31.5°C | 0.5°C | 43 mm | 63% | 2.6 m/s | 4.2 |
| 1990 | 22.0°C | 16.0°C | 9.9°C | 29.6°C | 2.2°C | 81 mm | 72% | 2.8 m/s | 3.8 |
| 1989 | 22.9°C | 16.8°C | 10.6°C | 29.9°C | -0.6°C | 58 mm | 67% | 2.6 m/s | 3.9 |
| 1988 | 22.8°C | 16.3°C | 9.9°C | 29.0°C | 5.8°C | 66 mm | 69% | 3 m/s | 4.1 |
| 1987 | 22.7°C | 16.8°C | 10.9°C | 29.3°C | 5.2°C | 45 mm | 73% | 2.4 m/s | 3.8 |
| 1986 🌧️ | 21.2°C | 15.4°C | 9.6°C | 26.8°C | 2.5°C | 176 mm | 78% | 2.7 m/s | 3.8 |
| 1985 | 23.4°C | 17.3°C | 11.3°C | 31.0°C | 3.3°C | 37 mm | 71% | 2.6 m/s | 4.2 |
| 1984 | 21.0°C | 15.0°C | 9.0°C | 27.8°C | 3.3°C | 81 mm | 71% | 2.5 m/s | 3.8 |
| 1983 | 24.3°C | 17.7°C | 11.2°C | 34.5°C | 3.9°C | 53 mm | 64% | 2.9 m/s | — |
| 1982 | 21.4°C | 15.5°C | 9.7°C | 30.6°C | 3.5°C | 95 mm | 75% | 2.3 m/s | — |
| 1981 | 19.9°C | 15.0°C | 10.2°C | 27.3°C | 1.2°C | 114 mm | 78% | 2.7 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 23.2°C with lows near 11.1°C (mean 17.2°C), based on 45 years of NASA POWER data.
September averages 70 mm of rainfall in Guelph, a relatively wet time of year. The wettest on record was 176 mm in 1986.
The hottest September reached 35.5°C in 2002. The coldest dipped to -1°C in 1993.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.6°C. Daytime highs moved from 22°C to 24.8°C and overnight lows from 10.3°C to 12.6°C over the same span.
September is one of the warmer months of the year in Guelph and a relatively wet time of year, so plan for around 23.2°C daytime highs and 11.1°C at night.
Not quite — September is the 9th coolest month in Guelph, averaging 17.2°C.
For September in Guelph, pack light layers you can adjust through the day, with typical highs of 23.2°C and lows of 11.1°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 71% — moderately humid.
Average wind speed in September is 2.6 m/s. The windiest September on record averaged 3.1 m/s (2010).
The wettest September on record was 1986 with 176 mm. On average, September sees 70 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 Guelph 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.
