September is one of the warmer months of the year in Chicago Heights, with average highs near 24.2°C and lows around 13.2°C (mean 18.7°C). It is about average for rainfall, averaging 79 mm of rainfall and 72% relative humidity across the period.
September is one of the warmer months of the year in Chicago Heights. Across 45 years of records, the warmest September in Chicago Heights was 2005 — when the month averaged 21.5°C — while the coldest was 1993 at 14.6°C. Typical September days reach 24.2°C with nights near 13.2°C. The long-term trend is warming, about 0.7°C per decade.
September is about average for rainfall in Chicago Heights, averaging 79 mm of rainfall. The wettest September on record was 2008 with 279 mm, while the driest was 2004 at 18 mm.
Relative humidity in Chicago Heights during September averages 72%. The most humid September was 1993 at 83%, and the least humid was 1999 at 59%.
September receives about 4.3 kWh/m²/day of solar energy in Chicago Heights. The sunniest September was 2004 at 5.2 kWh/m²/day, and the cloudiest was 1993 at 3.3.
Average wind speed in Chicago Heights during September is 2.8 m/s. The windiest Septembers were 1985, 2000 and 2010 at 3.4 m/s, while the calmest was 2025 at 2.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 17.8°C | 17.7°C | 18.9°C | 19.5°C | 20.1°C | +2.3°C |
| Avg High | 23.4°C | 23.2°C | 24.5°C | 24.7°C | 26.1°C | +2.7°C |
| Avg Low | 12.2°C | 12.2°C | 13.4°C | 14.3°C | 14.2°C | +2°C |
| Avg Rain | 86 mm | 78 mm | 84 mm | 81 mm | 57 mm | -29 mm |
September temperatures in Chicago Heights have risen by about 2.7°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 1.8°C (1989) to a record high of 35°C (2000).
Rainfall in September is about average for rainfall, averaging 79 mm, with a wettest year of 279 mm.
One of the best times to visit Chicago Heights
September is one of the best times to visit Chicago Heights. Expect days averaging 24.2°C and nights around 13.2°C (mean 18.7°C) — warmer than Chicago Heights's yearly average — with moderate rainfall (79 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 | 26.8°C | 20.4°C | 14.0°C | 31.7°C | 7.5°C | 42 mm | 65% | 2.1 m/s | 5 |
| 2024 | 27.2°C | 20.9°C | 14.6°C | 32.3°C | 8.3°C | 55 mm | 61% | 2.6 m/s | 4.8 |
| 2023 | 25.7°C | 20.0°C | 14.4°C | 33.2°C | 9.3°C | 81 mm | 71% | 2.5 m/s | 4 |
| 2022 | 25.4°C | 19.6°C | 13.9°C | 32.7°C | 5.8°C | 52 mm | 69% | 2.7 m/s | 4.4 |
| 2021 | 27.0°C | 21.0°C | 15.0°C | 32.5°C | 8.8°C | 39 mm | 66% | 3.2 m/s | 4.6 |
| 2020 | 24.2°C | 18.7°C | 13.1°C | 31.3°C | 5.1°C | 72 mm | 72% | 3.2 m/s | 4.1 |
| 2019 | 25.8°C | 21.0°C | 16.2°C | 29.9°C | 11.9°C | 189 mm | 79% | 2.8 m/s | 3.8 |
| 2018 | 25.8°C | 20.7°C | 15.5°C | 32.8°C | 6.2°C | 71 mm | 74% | 2.8 m/s | 4.4 |
| 2017 | 26.5°C | 20.4°C | 14.3°C | 33.8°C | 7.8°C | 29 mm | 67% | 2.5 m/s | 4.8 |
| 2016 | 24.8°C | 20.4°C | 15.9°C | 31.1°C | 10.2°C | 68 mm | 79% | 2.9 m/s | 4.4 |
| 2015 | 25.4°C | 20.3°C | 15.2°C | 32.2°C | 8.5°C | 96 mm | 76% | 2.7 m/s | 4.4 |
| 2014 | 22.6°C | 17.4°C | 12.1°C | 29.3°C | 5.4°C | 86 mm | 77% | 2.6 m/s | 4.4 |
| 2013 | 25.8°C | 19.9°C | 13.9°C | 35.0°C | 7.4°C | 56 mm | 70% | 2.8 m/s | 4.7 |
| 2012 | 24.0°C | 18.4°C | 12.8°C | 31.4°C | 3.6°C | 52 mm | 70% | 2.9 m/s | 4.7 |
| 2011 | 21.8°C | 17.3°C | 12.8°C | 34.9°C | 7.5°C | 93 mm | 74% | 3.1 m/s | 3.9 |
| 2010 | 24.0°C | 18.9°C | 13.8°C | 31.1°C | 9.3°C | 72 mm | 72% | 3.4 m/s | 4.3 |
| 2009 | 23.8°C | 18.7°C | 13.6°C | 28.4°C | 6.9°C | 27 mm | 77% | 2.3 m/s | 4.3 |
| 2008 🌧️ | 23.7°C | 18.8°C | 14.0°C | 33.9°C | 8.2°C | 279 mm | 80% | 2.4 m/s | 3.9 |
| 2007 | 25.0°C | 19.3°C | 13.6°C | 30.4°C | 6.2°C | 32 mm | 74% | 2.9 m/s | 5.1 |
| 2006 | 21.8°C | 16.8°C | 11.8°C | 28.2°C | 5.9°C | 115 mm | 79% | 2.8 m/s | 3.8 |
| 2005 🔥 | 27.4°C | 21.5°C | 15.6°C | 33.7°C | 6.0°C | 72 mm | 67% | 2.8 m/s | 4.4 |
| 2004 | 25.3°C | 19.7°C | 14.0°C | 29.2°C | 7.9°C | 18 mm | 71% | 2.6 m/s | 5.2 |
| 2003 | 23.6°C | 17.8°C | 12.0°C | 29.0°C | 4.6°C | 61 mm | 70% | 3 m/s | 4.5 |
| 2002 | 27.2°C | 20.7°C | 14.2°C | 34.1°C | 6.3°C | 56 mm | 65% | 2.5 m/s | 4.7 |
| 2001 | 22.7°C | 17.3°C | 11.9°C | 30.1°C | 6.1°C | 83 mm | 74% | 3 m/s | 4.4 |
| 2000 | 24.4°C | 18.6°C | 12.8°C | 35.0°C | 4.8°C | 100 mm | 68% | 3.4 m/s | 4.1 |
| 1999 | 25.4°C | 18.7°C | 12.0°C | 34.0°C | 4.4°C | 47 mm | 59% | 3 m/s | 4.9 |
| 1998 | 26.3°C | 20.6°C | 14.8°C | 32.6°C | 9.2°C | 62 mm | 70% | 2.7 m/s | 4.4 |
| 1997 | 23.6°C | 18.1°C | 12.6°C | 29.4°C | 6.7°C | 59 mm | 72% | 2.9 m/s | 4.4 |
| 1996 | 22.5°C | 17.4°C | 12.4°C | 29.2°C | 6.9°C | 86 mm | 75% | 2.5 m/s | 4.1 |
| 1995 | 22.8°C | 16.9°C | 10.9°C | 30.6°C | 2.6°C | 31 mm | 64% | 2.8 m/s | 4.4 |
| 1994 | 23.9°C | 18.2°C | 12.6°C | 30.6°C | 6.7°C | 50 mm | 71% | 2.6 m/s | 4.1 |
| 1993 ❄️ | 18.8°C | 14.6°C | 10.5°C | 23.7°C | 3.1°C | 171 mm | 83% | 3 m/s | 3.3 |
| 1992 | 22.1°C | 16.6°C | 11.2°C | 28.4°C | 3.7°C | 158 mm | 76% | 3 m/s | 4 |
| 1991 | 23.6°C | 17.7°C | 11.9°C | 31.5°C | 2.2°C | 66 mm | 66% | 2.8 m/s | 4.4 |
| 1990 | 23.4°C | 18.2°C | 13.0°C | 31.3°C | 3.6°C | 50 mm | 76% | 2.8 m/s | 4.2 |
| 1989 | 21.2°C | 16.0°C | 10.9°C | 27.9°C | 1.8°C | 113 mm | 77% | 2.6 m/s | 4.4 |
| 1988 | 25.9°C | 19.2°C | 12.5°C | 30.9°C | 7.2°C | 54 mm | 63% | 3.1 m/s | 4.1 |
| 1987 | 22.7°C | 17.6°C | 12.5°C | 28.5°C | 7.3°C | 59 mm | 77% | 2.5 m/s | 3.9 |
| 1986 | 24.5°C | 19.1°C | 13.7°C | 28.7°C | 6.1°C | 167 mm | 75% | 3 m/s | 3.7 |
| 1985 | 23.8°C | 18.4°C | 13.0°C | 32.2°C | 4.6°C | 63 mm | 70% | 3.4 m/s | 3.8 |
| 1984 | 23.0°C | 17.0°C | 11.0°C | 31.2°C | 3.1°C | 74 mm | 68% | 3.1 m/s | 3.6 |
| 1983 | 24.6°C | 18.3°C | 12.0°C | 33.5°C | 2.2°C | 90 mm | 66% | 2.9 m/s | — |
| 1982 | 23.3°C | 17.7°C | 12.0°C | 29.1°C | 5.7°C | 54 mm | 74% | 2.7 m/s | — |
| 1981 | 22.0°C | 17.0°C | 12.1°C | 27.9°C | 4.5°C | 101 mm | 77% | 3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 24.2°C with lows near 13.2°C (mean 18.7°C), based on 45 years of NASA POWER data.
September averages 79 mm of rainfall in Chicago Heights, about average for rainfall. The wettest on record was 279 mm in 2008.
The hottest September reached 35°C in 2000. 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 2.7°C. Daytime highs moved from 23.3°C to 26.4°C and overnight lows from 12°C to 14.4°C over the same span.
September is one of the warmer months of the year in Chicago Heights and about average for rainfall, so plan for around 24.2°C daytime highs and 13.2°C at night.
Not quite — September is the 9th coolest month in Chicago Heights, averaging 18.7°C.
For September in Chicago Heights, pack light layers you can adjust through the day, with typical highs of 24.2°C and lows of 13.2°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 72% — moderately humid.
Average wind speed in September is 2.8 m/s. The windiest September on record averaged 3.4 m/s (1985).
The wettest September on record was 2008 with 279 mm. On average, September sees 79 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 Chicago Heights 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.
