September is one of the warmer months of the year in Decatur, with average highs near 26.1°C and lows around 13.3°C (mean 19.7°C). It is about average for rainfall, averaging 76 mm of rainfall and 69% relative humidity across the period.
September is one of the warmer months of the year in Decatur. Across 45 years of records, the warmest September in Decatur was 2019 — when the month averaged 22.9°C — while the coldest was 1993 at 15.7°C. Typical September days reach 26.1°C with nights near 13.3°C. The long-term trend is warming, about 0.5°C per decade.
September is about average for rainfall in Decatur, averaging 76 mm of rainfall. The wettest September on record was 2008 with 249 mm, while the driest was 2004 at 14 mm.
Relative humidity in Decatur during September averages 69%. The most humid September was 1993 at 83%, and the least humid was 1999 at 55%.
September receives about 4.6 kWh/m²/day of solar energy in Decatur. The sunniest September was 2004 at 5.4 kWh/m²/day, and the cloudiest was 1993 at 3.4.
Average wind speed in Decatur during September is 2.5 m/s. The windiest September was 1985 at 3.2 m/s, while the calmest was 2025 at 1.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 19.4°C | 18.8°C | 19.7°C | 20.3°C | 20.8°C | +1.4°C |
| Avg High | 25.7°C | 25.3°C | 26.1°C | 26.4°C | 27.4°C | +1.7°C |
| Avg Low | 13.0°C | 12.3°C | 13.3°C | 14.2°C | 14.2°C | +1.2°C |
| Avg Rain | 75 mm | 69 mm | 79 mm | 87 mm | 63 mm | -11 mm |
September temperatures in Decatur have risen by about 2.2°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -0.3°C (1995) to a record high of 39.1°C (2011).
Rainfall in September is about average for rainfall, averaging 76 mm, with a wettest year of 249 mm.
One of the best times to visit Decatur
September is one of the best times to visit Decatur. Expect days averaging 26.1°C and nights around 13.3°C (mean 19.7°C) — warmer than Decatur's yearly average — with moderate rainfall (76 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 | 29.8°C | 22.3°C | 14.9°C | 36.1°C | 7.6°C | 28 mm | 56% | 1.8 m/s | 5.1 |
| 2024 | 28.1°C | 21.3°C | 14.5°C | 33.6°C | 7.8°C | 98 mm | 62% | 2.2 m/s | 4.6 |
| 2023 | 27.9°C | 21.4°C | 14.8°C | 34.5°C | 9.0°C | 53 mm | 65% | 2.1 m/s | 4.6 |
| 2022 | 26.3°C | 19.9°C | 13.5°C | 33.7°C | 4.1°C | 53 mm | 69% | 2.4 m/s | 4.6 |
| 2021 | 26.6°C | 20.5°C | 14.5°C | 31.2°C | 8.0°C | 90 mm | 73% | 2.7 m/s | 5 |
| 2020 | 25.7°C | 19.4°C | 13.1°C | 31.2°C | 5.0°C | 56 mm | 72% | 2.5 m/s | 4.4 |
| 2019 🔥 | 28.7°C | 22.9°C | 17.1°C | 32.5°C | 11.9°C | 78 mm | 73% | 2.6 m/s | 4.9 |
| 2018 | 27.0°C | 21.2°C | 15.5°C | 33.0°C | 6.0°C | 105 mm | 76% | 2.4 m/s | 4.6 |
| 2017 | 28.7°C | 21.6°C | 14.6°C | 34.7°C | 8.1°C | 21 mm | 61% | 2.3 m/s | 5 |
| 2016 | 26.0°C | 21.0°C | 15.9°C | 31.6°C | 10.0°C | 96 mm | 79% | 2.4 m/s | 4.8 |
| 2015 | 26.7°C | 20.8°C | 14.9°C | 33.3°C | 6.8°C | 99 mm | 74% | 2.5 m/s | 4.8 |
| 2014 | 24.1°C | 18.1°C | 12.2°C | 31.5°C | 5.6°C | 138 mm | 75% | 2.3 m/s | 4.6 |
| 2013 | 28.2°C | 21.2°C | 14.2°C | 36.1°C | 7.5°C | 34 mm | 66% | 2.4 m/s | 4.9 |
| 2012 | 24.8°C | 18.7°C | 12.7°C | 32.2°C | 4.1°C | 111 mm | 71% | 2.6 m/s | 4.5 |
| 2011 | 24.9°C | 18.5°C | 12.0°C | 39.1°C | 4.8°C | 60 mm | 66% | 2.9 m/s | 4.1 |
| 2010 | 24.4°C | 18.7°C | 13.1°C | 30.0°C | 7.5°C | 132 mm | 78% | 2.7 m/s | 4.8 |
| 2009 | 23.7°C | 18.4°C | 13.0°C | 26.2°C | 7.9°C | 61 mm | 80% | 2.2 m/s | 4.4 |
| 2008 🌧️ | 24.3°C | 18.9°C | 13.4°C | 30.4°C | 7.8°C | 249 mm | 81% | 2.1 m/s | 4.2 |
| 2007 | 29.1°C | 22.0°C | 14.9°C | 35.6°C | 4.3°C | 42 mm | 62% | 2.6 m/s | 4.9 |
| 2006 | 24.4°C | 18.3°C | 12.2°C | 31.1°C | 4.5°C | 62 mm | 70% | 2.5 m/s | 4 |
| 2005 | 29.2°C | 22.5°C | 15.8°C | 35.0°C | 5.7°C | 91 mm | 64% | 2.4 m/s | 4.7 |
| 2004 | 27.2°C | 20.5°C | 13.7°C | 30.4°C | 7.5°C | 14 mm | 66% | 2.4 m/s | 5.4 |
| 2003 | 23.9°C | 17.8°C | 11.6°C | 29.4°C | 2.9°C | 74 mm | 71% | 2.5 m/s | 4.8 |
| 2002 | 27.1°C | 20.5°C | 13.8°C | 32.7°C | 5.2°C | 50 mm | 68% | 2.2 m/s | 4.8 |
| 2001 | 25.2°C | 18.5°C | 11.8°C | 31.7°C | 3.2°C | 66 mm | 68% | 2.6 m/s | 4.9 |
| 2000 | 26.5°C | 19.4°C | 12.3°C | 35.2°C | 4.1°C | 82 mm | 65% | 3 m/s | 4.5 |
| 1999 | 27.1°C | 19.3°C | 11.6°C | 34.4°C | 4.7°C | 48 mm | 55% | 2.5 m/s | 5.1 |
| 1998 | 27.3°C | 21.0°C | 14.6°C | 32.3°C | 7.9°C | 36 mm | 71% | 2.3 m/s | 4.6 |
| 1997 | 26.0°C | 19.4°C | 12.9°C | 32.6°C | 7.5°C | 72 mm | 67% | 2.5 m/s | 4.7 |
| 1996 | 25.7°C | 19.0°C | 12.3°C | 32.0°C | 5.5°C | 57 mm | 65% | 2.4 m/s | 4.5 |
| 1995 | 24.8°C | 17.8°C | 10.8°C | 30.7°C | -0.3°C | 22 mm | 63% | 2.5 m/s | 4.5 |
| 1994 | 25.3°C | 18.9°C | 12.4°C | 32.8°C | 6.9°C | 56 mm | 68% | 2.2 m/s | 4.5 |
| 1993 ❄️ | 20.7°C | 15.7°C | 10.6°C | 25.9°C | 0.6°C | 209 mm | 83% | 2.7 m/s | 3.4 |
| 1992 | 24.5°C | 17.9°C | 11.3°C | 30.3°C | 1.3°C | 78 mm | 72% | 2.6 m/s | 4.4 |
| 1991 | 25.3°C | 19.2°C | 13.0°C | 33.3°C | 1.4°C | 67 mm | 65% | 2.4 m/s | 4.6 |
| 1990 | 26.5°C | 20.2°C | 13.8°C | 35.7°C | 3.0°C | 46 mm | 68% | 2.5 m/s | 4.4 |
| 1989 | 22.8°C | 17.1°C | 11.3°C | 29.7°C | 1.0°C | 114 mm | 77% | 2.3 m/s | 4.3 |
| 1988 | 28.8°C | 21.4°C | 13.9°C | 33.2°C | 8.2°C | 48 mm | 56% | 2.9 m/s | 4.4 |
| 1987 | 27.2°C | 20.3°C | 13.5°C | 33.3°C | 7.9°C | 37 mm | 64% | 2.5 m/s | 4.5 |
| 1986 | 26.8°C | 21.2°C | 15.6°C | 30.2°C | 6.5°C | 199 mm | 74% | 2.7 m/s | 4.1 |
| 1985 | 26.0°C | 19.7°C | 13.4°C | 32.8°C | 4.1°C | 26 mm | 68% | 3.2 m/s | 4.5 |
| 1984 | 24.7°C | 18.4°C | 12.1°C | 36.9°C | 1.3°C | 103 mm | 66% | 3 m/s | 4 |
| 1983 | 27.6°C | 20.4°C | 13.2°C | 36.1°C | 1.4°C | 39 mm | 59% | 2.8 m/s | — |
| 1982 | 24.5°C | 18.6°C | 12.7°C | 29.7°C | 4.8°C | 53 mm | 74% | 2.4 m/s | — |
| 1981 | 22.9°C | 17.3°C | 11.7°C | 28.5°C | 4.3°C | 53 mm | 78% | 2.6 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 26.1°C with lows near 13.3°C (mean 19.7°C), based on 45 years of NASA POWER data.
September averages 76 mm of rainfall in Decatur, about average for rainfall. The wettest on record was 249 mm in 2008.
The hottest September reached 39.1°C in 2011. The coldest dipped to -0.3°C in 1995.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.2°C. Daytime highs moved from 25.1°C to 27.7°C and overnight lows from 12.6°C to 14.4°C over the same span.
September is one of the warmer months of the year in Decatur and about average for rainfall, so plan for around 26.1°C daytime highs and 13.3°C at night.
Not quite — September is the 9th coolest month in Decatur, averaging 19.7°C.
For September in Decatur, pack light layers you can adjust through the day, with typical highs of 26.1°C and lows of 13.3°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 69% — moderately humid.
Average wind speed in September is 2.5 m/s. The windiest September on record averaged 3.2 m/s (1985).
The wettest September on record was 2008 with 249 mm. On average, September sees 76 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 Decatur 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.
