September is one of the warmer months of the year in Windsor, with average highs near 23.1°C and lows around 12.2°C (mean 17.7°C). It is a relatively wet time of year, averaging 81 mm of rainfall and 74% relative humidity across the period.
September is one of the warmer months of the year in Windsor. Across 45 years of records, the warmest September in Windsor was 2002 — when the month averaged 20.1°C — while the coldest was 1993 at 14.5°C. Typical September days reach 23.1°C with nights near 12.2°C. The long-term trend is warming, about 0.7°C per decade.
September is a relatively wet time of year in Windsor, averaging 81 mm of rainfall. The wettest September on record was 1986 with 203 mm, while the driest was 2004 at 19 mm.
Relative humidity in Windsor during September averages 74%. The most humid September was 2011 at 81%, and the least humid was 1999 at 64%.
September receives about 4.2 kWh/m²/day of solar energy in Windsor. The sunniest Septembers were 1999, 2004 and 2025 at 4.8 kWh/m²/day, and the cloudiest was 1993 at 3.2.
Average wind speed in Windsor during September is 2.8 m/s. The windiest September was 2010 at 3.5 m/s, while the calmest was 2025 at 2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.7°C | 16.9°C | 18.1°C | 18.3°C | 18.8°C | +2.1°C |
| Avg High | 22.1°C | 22.5°C | 23.6°C | 23.5°C | 24.4°C | +2.3°C |
| Avg Low | 11.3°C | 11.3°C | 12.5°C | 13.1°C | 13.3°C | +2°C |
| Avg Rain | 110 mm | 78 mm | 76 mm | 78 mm | 59 mm | -51 mm |
September temperatures in Windsor have risen by about 2.7°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 0.3°C (1991) to a record high of 33.6°C (2002).
Rainfall in September is a relatively wet time of year, averaging 81 mm, with a wettest year of 203 mm.
One of the best times to visit Windsor
September is one of the best times to visit Windsor. Expect days averaging 23.1°C and nights around 12.2°C (mean 17.7°C) — warmer than Windsor's yearly average — with higher rainfall (81 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 | 26.1°C | 19.8°C | 13.5°C | 30.6°C | 7.2°C | 31 mm | 66% | 2 m/s | 4.8 |
| 2024 | 25.7°C | 20.0°C | 14.3°C | 30.0°C | 6.2°C | 34 mm | 73% | 2.5 m/s | 4.4 |
| 2023 | 23.6°C | 18.6°C | 13.6°C | 31.1°C | 9.7°C | 50 mm | 77% | 2.2 m/s | 4 |
| 2022 | 24.5°C | 18.9°C | 13.4°C | 31.2°C | 5.7°C | 38 mm | 71% | 2.7 m/s | 4.1 |
| 2021 | 23.9°C | 18.5°C | 13.1°C | 29.7°C | 7.5°C | 135 mm | 75% | 3.1 m/s | 4.4 |
| 2020 | 22.7°C | 17.3°C | 11.9°C | 28.5°C | 4.6°C | 63 mm | 76% | 3 m/s | 4.3 |
| 2019 | 24.3°C | 19.5°C | 14.7°C | 29.2°C | 11.3°C | 94 mm | 80% | 2.7 m/s | 4 |
| 2018 | 24.5°C | 19.6°C | 14.8°C | 31.9°C | 5.5°C | 95 mm | 80% | 2.8 m/s | 3.8 |
| 2017 | 24.5°C | 18.9°C | 13.3°C | 32.1°C | 7.0°C | 26 mm | 76% | 2.3 m/s | 4.5 |
| 2016 | 25.0°C | 19.9°C | 14.8°C | 31.7°C | 10.6°C | 100 mm | 76% | 2.8 m/s | 4.4 |
| 2015 | 25.1°C | 19.9°C | 14.6°C | 31.4°C | 8.0°C | 65 mm | 75% | 2.7 m/s | 4.5 |
| 2014 | 22.0°C | 16.7°C | 11.4°C | 30.2°C | 6.3°C | 98 mm | 77% | 2.5 m/s | 4.3 |
| 2013 | 22.6°C | 17.1°C | 11.7°C | 32.5°C | 6.1°C | 38 mm | 76% | 2.7 m/s | 4.4 |
| 2012 | 22.8°C | 17.2°C | 11.5°C | 30.9°C | 3.5°C | 58 mm | 70% | 2.8 m/s | 4.4 |
| 2011 | 21.4°C | 16.8°C | 12.2°C | 32.3°C | 4.9°C | 121 mm | 81% | 2.9 m/s | 3.6 |
| 2010 | 22.9°C | 17.5°C | 12.0°C | 32.3°C | 7.8°C | 85 mm | 71% | 3.5 m/s | 4 |
| 2009 | 22.9°C | 17.9°C | 13.0°C | 26.9°C | 6.0°C | 40 mm | 76% | 2.5 m/s | 4.5 |
| 2008 | 23.5°C | 18.2°C | 13.0°C | 32.1°C | 9.1°C | 167 mm | 78% | 2.5 m/s | 4.3 |
| 2007 | 24.4°C | 18.8°C | 13.1°C | 30.2°C | 6.1°C | 40 mm | 73% | 2.7 m/s | 4.6 |
| 2006 | 21.6°C | 16.4°C | 11.3°C | 28.2°C | 4.1°C | 67 mm | 77% | 3 m/s | 3.5 |
| 2005 | 25.8°C | 20.0°C | 14.1°C | 31.9°C | 6.7°C | 75 mm | 69% | 2.9 m/s | 4.5 |
| 2004 | 24.9°C | 19.2°C | 13.5°C | 28.7°C | 6.2°C | 19 mm | 72% | 2.6 m/s | 4.8 |
| 2003 | 22.7°C | 17.2°C | 11.6°C | 28.9°C | 4.6°C | 94 mm | 71% | 3 m/s | 4.5 |
| 2002 🔥 | 26.6°C | 20.1°C | 13.7°C | 33.6°C | 7.0°C | 41 mm | 67% | 2.7 m/s | 4.7 |
| 2001 | 21.8°C | 16.4°C | 11.0°C | 29.6°C | 4.5°C | 103 mm | 74% | 3.1 m/s | 4.3 |
| 2000 | 21.5°C | 16.3°C | 11.1°C | 30.8°C | 4.3°C | 118 mm | 76% | 3.3 m/s | 4 |
| 1999 | 24.8°C | 18.3°C | 11.9°C | 31.9°C | 4.8°C | 63 mm | 64% | 2.8 m/s | 4.8 |
| 1998 | 25.8°C | 19.9°C | 14.0°C | 31.4°C | 7.0°C | 41 mm | 68% | 2.8 m/s | 4.6 |
| 1997 | 22.0°C | 16.7°C | 11.3°C | 27.8°C | 5.9°C | 92 mm | 77% | 2.9 m/s | 4.1 |
| 1996 | 22.2°C | 17.2°C | 12.2°C | 29.6°C | 4.9°C | 101 mm | 76% | 3 m/s | 3.8 |
| 1995 | 22.0°C | 16.1°C | 10.1°C | 30.2°C | 0.9°C | 28 mm | 68% | 2.7 m/s | 4.4 |
| 1994 | 23.1°C | 17.4°C | 11.6°C | 30.5°C | 5.6°C | 70 mm | 72% | 2.7 m/s | 4.4 |
| 1993 ❄️ | 19.2°C | 14.5°C | 9.8°C | 28.0°C | 3.0°C | 124 mm | 78% | 2.9 m/s | 3.2 |
| 1992 | 20.9°C | 15.6°C | 10.3°C | 26.6°C | 2.0°C | 125 mm | 79% | 3.1 m/s | 4.2 |
| 1991 | 22.4°C | 16.5°C | 10.6°C | 31.4°C | 0.3°C | 25 mm | 68% | 2.8 m/s | 4.2 |
| 1990 | 22.4°C | 16.8°C | 11.3°C | 30.7°C | 3.7°C | 107 mm | 76% | 3 m/s | 4.1 |
| 1989 | 21.3°C | 16.1°C | 10.8°C | 28.0°C | 1.3°C | 93 mm | 78% | 2.6 m/s | 4.1 |
| 1988 | 23.0°C | 17.2°C | 11.4°C | 28.4°C | 6.0°C | 83 mm | 72% | 3.1 m/s | 4.1 |
| 1987 | 22.1°C | 17.0°C | 12.0°C | 27.7°C | 4.7°C | 88 mm | 79% | 2.4 m/s | 4.1 |
| 1986 🌧️ | 22.9°C | 17.3°C | 11.7°C | 27.1°C | 4.8°C | 203 mm | 79% | 2.9 m/s | 3.9 |
| 1985 | 22.5°C | 17.3°C | 12.1°C | 29.7°C | 4.2°C | 96 mm | 76% | 2.8 m/s | 4.1 |
| 1984 | 21.0°C | 15.5°C | 10.1°C | 31.9°C | 4.6°C | 85 mm | 73% | 2.8 m/s | 3.9 |
| 1983 | 24.0°C | 17.8°C | 11.6°C | 32.5°C | 3.6°C | 65 mm | 69% | 2.9 m/s | — |
| 1982 | 22.1°C | 16.4°C | 10.8°C | 29.6°C | 4.1°C | 77 mm | 76% | 2.4 m/s | — |
| 1981 | 20.2°C | 15.7°C | 11.2°C | 27.7°C | 4.9°C | 199 mm | 79% | 3.1 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 23.1°C with lows near 12.2°C (mean 17.7°C), based on 45 years of NASA POWER data.
September averages 81 mm of rainfall in Windsor, a relatively wet time of year. The wettest on record was 203 mm in 1986.
The hottest September reached 33.6°C in 2002. The coldest dipped to 0.3°C in 1991.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.7°C. Daytime highs moved from 22°C to 24.8°C and overnight lows from 11.2°C to 13.6°C over the same span.
September is one of the warmer months of the year in Windsor and a relatively wet time of year, so plan for around 23.1°C daytime highs and 12.2°C at night.
Not quite — September is the 9th coolest month in Windsor, averaging 17.7°C.
For September in Windsor, pack light layers you can adjust through the day, with typical highs of 23.1°C and lows of 12.2°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 74% — moderately humid.
Average wind speed in September is 2.8 m/s. The windiest September on record averaged 3.5 m/s (2010).
The wettest September on record was 1986 with 203 mm. On average, September sees 81 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 Windsor 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.
