September is one of the warmer months of the year in Rockford, with average highs near 23.3°C and lows around 11.4°C (mean 17.4°C). It is about average for rainfall, averaging 87 mm of rainfall and 74% relative humidity across the period.
September is one of the warmer months of the year in Rockford. Across 45 years of records, the warmest September in Rockford was 2005 — when the month averaged 20.8°C — while the coldest was 1993 at 13.4°C. Typical September days reach 23.3°C with nights near 11.4°C. The long-term trend is warming, about 0.5°C per decade.
September is about average for rainfall in Rockford, averaging 87 mm of rainfall. The wettest September on record was 1986 with 232 mm, while the driest was 2017 at 10 mm.
Relative humidity in Rockford during September averages 74%. The most humid September was 2019 at 86%, and the least humid was 1988 at 63%.
September receives about 4.3 kWh/m²/day of solar energy in Rockford. The sunniest September was 2004 at 5.1 kWh/m²/day, and the cloudiest was 1986 at 3.2.
Average wind speed in Rockford during September is 2.6 m/s. The windiest September was 1985 at 3.2 m/s, while the calmest was 2009 at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.7°C | 16.6°C | 17.7°C | 17.7°C | 18.6°C | +1.9°C |
| Avg High | 22.7°C | 22.7°C | 23.7°C | 23.3°C | 24.7°C | +2°C |
| Avg Low | 10.8°C | 10.6°C | 11.6°C | 12.1°C | 12.5°C | +1.7°C |
| Avg Rain | 87 mm | 78 mm | 90 mm | 98 mm | 76 mm | -11 mm |
September temperatures in Rockford have risen by about 2.5°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -1.8°C (1984) to a record high of 35°C (2023).
Rainfall in September is about average for rainfall, averaging 87 mm, with a wettest year of 232 mm.
One of the best times to visit Rockford
September is one of the best times to visit Rockford. Expect days averaging 23.3°C and nights around 11.4°C (mean 17.4°C) — warmer than Rockford's yearly average — with higher rainfall (87 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 | 25.5°C | 19.2°C | 12.9°C | 30.5°C | 5.4°C | 47 mm | 71% | 2 m/s | 4.7 |
| 2024 | 26.6°C | 19.6°C | 12.6°C | 31.8°C | 6.0°C | 44 mm | 65% | 2.2 m/s | 4.9 |
| 2023 | 25.0°C | 19.4°C | 13.8°C | 35.0°C | 9.1°C | 101 mm | 73% | 2.4 m/s | 3.9 |
| 2022 | 23.2°C | 17.5°C | 11.9°C | 29.6°C | 2.4°C | 123 mm | 77% | 2.5 m/s | 4.3 |
| 2021 | 26.6°C | 19.8°C | 12.9°C | 32.0°C | 6.9°C | 28 mm | 67% | 2.7 m/s | 4.6 |
| 2020 | 21.0°C | 15.8°C | 10.6°C | 26.6°C | 5.5°C | 116 mm | 81% | 2.9 m/s | 3.7 |
| 2019 | 23.8°C | 19.1°C | 14.5°C | 28.0°C | 9.1°C | 228 mm | 86% | 2.7 m/s | 3.6 |
| 2018 | 23.2°C | 18.0°C | 12.8°C | 29.5°C | 1.1°C | 179 mm | 83% | 2.4 m/s | 4.1 |
| 2017 | 24.8°C | 18.5°C | 12.2°C | 32.4°C | 6.8°C | 10 mm | 73% | 2.3 m/s | 4.9 |
| 2016 | 24.1°C | 19.1°C | 14.1°C | 31.3°C | 7.3°C | 94 mm | 82% | 2.8 m/s | 4.3 |
| 2015 | 24.9°C | 19.6°C | 14.2°C | 33.0°C | 6.4°C | 120 mm | 77% | 2.5 m/s | 4.5 |
| 2014 | 22.0°C | 16.0°C | 10.1°C | 27.5°C | 3.0°C | 71 mm | 79% | 2.4 m/s | 4.5 |
| 2013 | 23.8°C | 17.8°C | 11.7°C | 33.3°C | 5.2°C | 57 mm | 77% | 2.5 m/s | 4.8 |
| 2012 | 23.6°C | 17.0°C | 10.3°C | 34.1°C | 1.3°C | 49 mm | 66% | 2.7 m/s | 4.8 |
| 2011 | 21.1°C | 15.8°C | 10.5°C | 32.3°C | 2.2°C | 106 mm | 75% | 2.8 m/s | 4.2 |
| 2010 | 21.2°C | 16.1°C | 10.9°C | 28.0°C | 4.2°C | 63 mm | 81% | 3 m/s | 4.2 |
| 2009 | 23.1°C | 17.4°C | 11.7°C | 27.1°C | 2.6°C | 43 mm | 79% | 1.9 m/s | 4.5 |
| 2008 | 22.3°C | 17.2°C | 12.2°C | 30.8°C | 5.3°C | 154 mm | 83% | 2.4 m/s | 3.9 |
| 2007 | 23.4°C | 17.3°C | 11.1°C | 29.6°C | 0.7°C | 47 mm | 78% | 2.8 m/s | 4.9 |
| 2006 | 21.0°C | 15.6°C | 10.2°C | 27.8°C | 3.0°C | 97 mm | 78% | 2.7 m/s | 3.8 |
| 2005 🔥 | 27.6°C | 20.8°C | 14.1°C | 33.8°C | 3.6°C | 82 mm | 65% | 2.8 m/s | 4.4 |
| 2004 | 25.8°C | 19.0°C | 12.2°C | 30.1°C | 5.5°C | 14 mm | 69% | 2.5 m/s | 5.1 |
| 2003 | 24.1°C | 17.6°C | 11.0°C | 33.1°C | 1.9°C | 56 mm | 65% | 3 m/s | 4.5 |
| 2002 | 25.5°C | 18.9°C | 12.3°C | 32.2°C | 3.6°C | 86 mm | 71% | 2.3 m/s | 4.7 |
| 2001 | 21.7°C | 15.8°C | 9.9°C | 31.3°C | 1.0°C | 179 mm | 78% | 2.7 m/s | 4.3 |
| 2000 | 22.9°C | 16.9°C | 10.9°C | 33.5°C | 2.9°C | 140 mm | 72% | 3.1 m/s | 4.2 |
| 1999 | 23.9°C | 16.8°C | 9.8°C | 32.9°C | 3.7°C | 97 mm | 64% | 2.7 m/s | 4.7 |
| 1998 | 25.5°C | 18.9°C | 12.4°C | 31.9°C | 7.4°C | 69 mm | 71% | 2.3 m/s | 4.6 |
| 1997 | 23.8°C | 17.5°C | 11.2°C | 30.1°C | 5.0°C | 64 mm | 72% | 2.7 m/s | 4.2 |
| 1996 | 22.3°C | 16.6°C | 10.9°C | 29.1°C | 5.6°C | 47 mm | 73% | 2.4 m/s | 4.3 |
| 1995 | 21.9°C | 15.6°C | 9.3°C | 30.1°C | 0.4°C | 48 mm | 68% | 2.7 m/s | 4.2 |
| 1994 | 23.3°C | 17.8°C | 12.2°C | 30.8°C | 4.6°C | 65 mm | 76% | 2.4 m/s | 4 |
| 1993 ❄️ | 18.4°C | 13.4°C | 8.4°C | 24.5°C | -0.3°C | 113 mm | 83% | 2.8 m/s | 3.3 |
| 1992 | 21.2°C | 15.4°C | 9.6°C | 28.0°C | -0.3°C | 146 mm | 77% | 2.8 m/s | 3.8 |
| 1991 | 22.5°C | 16.4°C | 10.2°C | 32.5°C | -0.2°C | 99 mm | 69% | 2.8 m/s | 4.2 |
| 1990 | 23.7°C | 17.7°C | 11.6°C | 32.0°C | 3.1°C | 35 mm | 74% | 2.7 m/s | 4.3 |
| 1989 | 21.0°C | 15.2°C | 9.3°C | 27.8°C | 1.4°C | 54 mm | 76% | 2.4 m/s | 4.4 |
| 1988 | 25.8°C | 18.6°C | 11.4°C | 31.9°C | 4.9°C | 74 mm | 63% | 3.1 m/s | 4.1 |
| 1987 | 21.4°C | 16.2°C | 11.1°C | 26.6°C | 6.3°C | 65 mm | 81% | 2.3 m/s | 4 |
| 1986 🌧️ | 22.8°C | 17.6°C | 12.4°C | 27.7°C | 4.1°C | 232 mm | 79% | 2.7 m/s | 3.2 |
| 1985 | 23.1°C | 17.6°C | 12.2°C | 33.8°C | 2.7°C | 82 mm | 73% | 3.2 m/s | 3.5 |
| 1984 | 23.2°C | 16.4°C | 9.6°C | 32.8°C | -1.8°C | 77 mm | 66% | 3 m/s | 3.9 |
| 1983 | 23.8°C | 17.2°C | 10.6°C | 32.8°C | 1.5°C | 86 mm | 69% | 2.9 m/s | — |
| 1982 | 22.4°C | 16.4°C | 10.5°C | 29.1°C | 2.7°C | 32 mm | 75% | 2.8 m/s | — |
| 1981 | 21.0°C | 15.4°C | 9.7°C | 27.0°C | 1.4°C | 85 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 23.3°C with lows near 11.4°C (mean 17.4°C), based on 45 years of NASA POWER data.
September averages 87 mm of rainfall in Rockford, about average for rainfall. The wettest on record was 232 mm in 1986.
The hottest September reached 35°C in 2023. The coldest dipped to -1.8°C in 1984.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.5°C. Daytime highs moved from 22.7°C to 25.4°C and overnight lows from 10.5°C to 12.8°C over the same span.
September is one of the warmer months of the year in Rockford and about average for rainfall, so plan for around 23.3°C daytime highs and 11.4°C at night.
Not quite — September is the 9th coolest month in Rockford, averaging 17.4°C.
For September in Rockford, pack light layers you can adjust through the day, with typical highs of 23.3°C and lows of 11.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 74% — moderately humid.
Average wind speed in September is 2.6 m/s. The windiest September on record averaged 3.2 m/s (1985).
The wettest September on record was 1986 with 232 mm. On average, September sees 87 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 Rockford 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.
