September is one of the warmer months of the year in Belleville, with average highs near 20.7°C and lows around 13.7°C (mean 17.2°C). It is about average for rainfall, averaging 70 mm of rainfall and 73% relative humidity across the period.
September is one of the warmer months of the year in Belleville. Across 45 years of records, the warmest September in Belleville was 2015 — when the month averaged 20°C — while the coldest was 1995 at 13.6°C. Typical September days reach 20.7°C with nights near 13.7°C. The long-term trend is warming, about 0.9°C per decade.
September is about average for rainfall in Belleville, averaging 70 mm of rainfall. The wettest September on record was 1986 with 163 mm, while the driest was 2023 at 14 mm.
Relative humidity in Belleville during September averages 73%. The most humid September was 1981 at 81%, and the least humid was 1983 at 67%.
September receives about 4 kWh/m²/day of solar energy in Belleville. The sunniest Septembers were 2016, 2017 and 2023, among others at 4.5 kWh/m²/day, and the cloudiest was 2006 at 3.2.
Average wind speed in Belleville during September is 2.4 m/s. The windiest September was 2010 at 3 m/s, while the calmest was 2017 at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.1°C | 15.7°C | 17.5°C | 18.6°C | 18.8°C | +2.7°C |
| Avg High | 19.6°C | 19.2°C | 21.0°C | 22.0°C | 22.3°C | +2.7°C |
| Avg Low | 12.6°C | 12.1°C | 13.9°C | 15.1°C | 15.3°C | +2.7°C |
| Avg Rain | 83 mm | 75 mm | 78 mm | 57 mm | 49 mm | -33 mm |
September temperatures in Belleville have risen by about 2.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 1.8°C (1989) to a record high of 30.1°C (2017).
Rainfall in September is about average for rainfall, averaging 70 mm, with a wettest year of 163 mm.
One of the best times to visit Belleville
September is one of the best times to visit Belleville. Expect days averaging 20.7°C and nights around 13.7°C (mean 17.2°C) — warmer than Belleville'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 | 22.6°C | 18.9°C | 15.2°C | 25.3°C | 10.7°C | 22 mm | 68% | 2 m/s | 4.4 |
| 2024 | 23.2°C | 19.6°C | 16.1°C | 27.0°C | 10.4°C | 65 mm | 74% | 2.3 m/s | 4.2 |
| 2023 | 23.0°C | 19.3°C | 15.5°C | 29.1°C | 10.2°C | 14 mm | 69% | 2.2 m/s | 4.5 |
| 2022 | 21.4°C | 18.1°C | 14.7°C | 26.5°C | 7.1°C | 54 mm | 72% | 2.4 m/s | 3.7 |
| 2021 | 22.6°C | 19.1°C | 15.7°C | 25.6°C | 9.9°C | 95 mm | 69% | 2.7 m/s | 3.9 |
| 2020 | 21.1°C | 17.8°C | 14.5°C | 26.0°C | 6.9°C | 45 mm | 71% | 2.5 m/s | 4 |
| 2019 | 21.7°C | 18.2°C | 14.8°C | 25.7°C | 11.0°C | 56 mm | 73% | 2.4 m/s | 4 |
| 2018 | 22.8°C | 19.5°C | 16.2°C | 29.4°C | 9.0°C | 61 mm | 74% | 2.4 m/s | 4.1 |
| 2017 | 23.2°C | 19.3°C | 15.5°C | 30.1°C | 9.7°C | 41 mm | 71% | 1.9 m/s | 4.5 |
| 2016 | 23.3°C | 19.8°C | 16.3°C | 27.8°C | 9.4°C | 39 mm | 68% | 2.4 m/s | 4.5 |
| 2015 🔥 | 23.4°C | 20.0°C | 16.6°C | 28.8°C | 10.4°C | 82 mm | 73% | 2.3 m/s | 4.2 |
| 2014 | 20.9°C | 17.3°C | 13.6°C | 26.3°C | 6.7°C | 39 mm | 74% | 2.4 m/s | 4.3 |
| 2013 | 20.8°C | 17.2°C | 13.5°C | 27.5°C | 7.2°C | 52 mm | 69% | 2.5 m/s | 4.2 |
| 2012 | 21.4°C | 17.9°C | 14.4°C | 27.6°C | 9.2°C | 55 mm | 69% | 2.6 m/s | 4 |
| 2011 | 22.0°C | 18.8°C | 15.5°C | 28.8°C | 8.0°C | 74 mm | 75% | 2.5 m/s | 3.9 |
| 2010 | 20.8°C | 17.6°C | 14.4°C | 28.6°C | 9.5°C | 66 mm | 72% | 3 m/s | 3.5 |
| 2009 | 21.4°C | 17.7°C | 14.0°C | 25.0°C | 7.0°C | 58 mm | 70% | 2.5 m/s | 4.5 |
| 2008 | 21.2°C | 17.8°C | 14.4°C | 27.6°C | 9.1°C | 61 mm | 74% | 2.3 m/s | 3.8 |
| 2007 | 22.0°C | 18.3°C | 14.6°C | 28.9°C | 8.6°C | 43 mm | 70% | 2.4 m/s | 4.5 |
| 2006 | 19.4°C | 16.4°C | 13.3°C | 24.1°C | 7.4°C | 121 mm | 78% | 2.8 m/s | 3.2 |
| 2005 | 23.1°C | 19.4°C | 15.7°C | 27.5°C | 9.0°C | 95 mm | 72% | 2.6 m/s | 4.5 |
| 2004 | 21.8°C | 18.3°C | 14.8°C | 26.2°C | 8.1°C | 108 mm | 77% | 2.2 m/s | 4.5 |
| 2003 | 19.8°C | 16.4°C | 13.1°C | 25.7°C | 7.3°C | 79 mm | 77% | 2.4 m/s | 3.9 |
| 2002 | 22.0°C | 18.4°C | 14.7°C | 27.7°C | 10.0°C | 53 mm | 72% | 2.1 m/s | 4.3 |
| 2001 | 19.6°C | 15.8°C | 12.0°C | 26.6°C | 6.6°C | 79 mm | 73% | 2.1 m/s | 4.3 |
| 2000 | 19.7°C | 16.1°C | 12.6°C | 27.1°C | 3.2°C | 80 mm | 74% | 2.7 m/s | 4.1 |
| 1999 | 21.7°C | 18.2°C | 14.7°C | 28.2°C | 5.8°C | 86 mm | 73% | 2.4 m/s | 3.9 |
| 1998 | 21.5°C | 18.1°C | 14.6°C | 27.5°C | 7.8°C | 64 mm | 73% | 2.4 m/s | 4.2 |
| 1997 | 19.7°C | 16.2°C | 12.6°C | 23.8°C | 5.3°C | 102 mm | 74% | 2.8 m/s | 3.6 |
| 1996 | 19.3°C | 16.0°C | 12.8°C | 26.2°C | 6.2°C | 128 mm | 79% | 2.3 m/s | 3.6 |
| 1995 ❄️ | 17.4°C | 13.6°C | 9.8°C | 22.9°C | 6.2°C | 53 mm | 73% | 2.2 m/s | 4.1 |
| 1994 | 19.1°C | 15.4°C | 11.6°C | 23.6°C | 6.2°C | 55 mm | 75% | 2.4 m/s | 3.9 |
| 1993 | 17.7°C | 14.2°C | 10.8°C | 24.0°C | 2.9°C | 79 mm | 74% | 2.5 m/s | 3.4 |
| 1992 | 18.1°C | 14.7°C | 11.3°C | 23.1°C | 4.3°C | 79 mm | 78% | 2.5 m/s | 3.8 |
| 1991 | 18.7°C | 15.1°C | 11.4°C | 25.0°C | 3.4°C | 53 mm | 68% | 2.4 m/s | 4.1 |
| 1990 | 18.6°C | 15.0°C | 11.4°C | 25.8°C | 5.0°C | 52 mm | 76% | 2.3 m/s | 3.3 |
| 1989 | 19.5°C | 15.8°C | 12.1°C | 25.8°C | 1.8°C | 72 mm | 75% | 2.1 m/s | 3.9 |
| 1988 | 19.0°C | 15.2°C | 11.5°C | 23.4°C | 6.8°C | 53 mm | 73% | 2.5 m/s | 4.2 |
| 1987 | 18.5°C | 15.3°C | 12.0°C | 22.8°C | 7.0°C | 86 mm | 79% | 2.3 m/s | 3.7 |
| 1986 🌧️ | 18.6°C | 15.4°C | 12.2°C | 23.9°C | 6.1°C | 163 mm | 78% | 2.5 m/s | 3.4 |
| 1985 | 21.4°C | 17.7°C | 14.1°C | 27.2°C | 7.9°C | 61 mm | 72% | 2.3 m/s | 4 |
| 1984 | 19.1°C | 15.6°C | 12.1°C | 23.5°C | 5.8°C | 59 mm | 72% | 2.6 m/s | 4.1 |
| 1983 | 22.2°C | 18.5°C | 14.8°C | 29.1°C | 8.2°C | 53 mm | 67% | 2.8 m/s | — |
| 1982 | 19.7°C | 16.0°C | 12.3°C | 25.8°C | 8.0°C | 61 mm | 74% | 2.2 m/s | — |
| 1981 | 18.1°C | 15.1°C | 12.1°C | 25.2°C | 2.6°C | 134 mm | 81% | 2.8 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 20.7°C with lows near 13.7°C (mean 17.2°C), based on 45 years of NASA POWER data.
September averages 70 mm of rainfall in Belleville, about average for rainfall. The wettest on record was 163 mm in 1986.
The hottest September reached 30.1°C in 2017. The coldest dipped to 1.8°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.4°C. Daytime highs moved from 20.1°C to 22.6°C and overnight lows from 13.1°C to 15.4°C over the same span.
September is one of the warmer months of the year in Belleville and about average for rainfall, so plan for around 20.7°C daytime highs and 13.7°C at night.
Not quite — September is the 10th coolest month in Belleville, averaging 17.2°C.
For September in Belleville, pack light layers you can adjust through the day, with typical highs of 20.7°C and lows of 13.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 73% — moderately humid.
Average wind speed in September is 2.4 m/s. The windiest September on record averaged 3 m/s (2010).
The wettest September on record was 1986 with 163 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 Belleville 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.
