September is one of the warmer months of the year in Plainfield, with average highs near 24.9°C and lows around 12.6°C (mean 18.8°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 Plainfield. Across 45 years of records, the warmest September in Plainfield was 2005 — when the month averaged 21.8°C — while the coldest was 1993 at 14.6°C. Typical September days reach 24.9°C with nights near 12.6°C. The long-term trend is warming, about 0.6°C per decade.
September is about average for rainfall in Plainfield, averaging 79 mm of rainfall. The wettest September on record was 2008 with 275 mm, while the driest was 2004 at 18 mm.
Relative humidity in Plainfield during September averages 72%. The most humid September was 2019 at 83%, and the least humid was 1999 at 59%.
September receives about 4.4 kWh/m²/day of solar energy in Plainfield. The sunniest September was 2004 at 5.3 kWh/m²/day, and the cloudiest was 1993 at 3.3.
Average wind speed in Plainfield during September is 2.6 m/s. The windiest September was 1985 at 3.3 m/s, while the calmest was 2025 at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 18.1°C | 17.8°C | 18.9°C | 19.2°C | 20.0°C | +1.9°C |
| Avg High | 24.3°C | 24.0°C | 25.2°C | 24.9°C | 26.6°C | +2.3°C |
| Avg Low | 11.9°C | 11.6°C | 12.7°C | 13.5°C | 13.4°C | +1.5°C |
| Avg Rain | 82 mm | 76 mm | 84 mm | 85 mm | 58 mm | -24 mm |
September temperatures in Plainfield have risen by about 2.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 0.3°C (1984) to a record high of 36.1°C (2000).
Rainfall in September is about average for rainfall, averaging 79 mm, with a wettest year of 275 mm.
One of the best times to visit Plainfield
September is one of the best times to visit Plainfield. Expect days averaging 24.9°C and nights around 12.6°C (mean 18.8°C) — warmer than Plainfield'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 | 27.7°C | 20.5°C | 13.3°C | 32.2°C | 6.5°C | 30 mm | 64% | 1.9 m/s | 5 |
| 2024 | 28.0°C | 20.9°C | 13.8°C | 33.2°C | 7.0°C | 29 mm | 60% | 2.3 m/s | 4.8 |
| 2023 | 26.4°C | 20.2°C | 13.9°C | 34.5°C | 8.6°C | 97 mm | 70% | 2.2 m/s | 4 |
| 2022 | 25.8°C | 19.3°C | 12.9°C | 33.8°C | 4.7°C | 52 mm | 70% | 2.4 m/s | 4.7 |
| 2021 | 28.0°C | 21.1°C | 14.3°C | 33.2°C | 7.5°C | 38 mm | 65% | 2.8 m/s | 4.7 |
| 2020 | 23.9°C | 18.0°C | 12.1°C | 31.4°C | 4.4°C | 99 mm | 75% | 2.8 m/s | 4 |
| 2019 | 25.6°C | 20.6°C | 15.7°C | 30.3°C | 10.7°C | 229 mm | 83% | 2.5 m/s | 3.9 |
| 2018 | 26.1°C | 20.3°C | 14.6°C | 33.4°C | 3.2°C | 76 mm | 76% | 2.5 m/s | 4.3 |
| 2017 | 27.3°C | 20.4°C | 13.6°C | 34.5°C | 7.1°C | 19 mm | 66% | 2.3 m/s | 5 |
| 2016 | 24.9°C | 20.1°C | 15.4°C | 31.2°C | 9.3°C | 71 mm | 81% | 2.7 m/s | 4.4 |
| 2015 | 25.6°C | 20.1°C | 14.5°C | 32.2°C | 6.9°C | 97 mm | 78% | 2.4 m/s | 4.5 |
| 2014 | 22.9°C | 17.2°C | 11.4°C | 29.8°C | 4.3°C | 86 mm | 78% | 2.3 m/s | 4.6 |
| 2013 | 26.3°C | 19.8°C | 13.2°C | 35.3°C | 7.4°C | 42 mm | 70% | 2.5 m/s | 5 |
| 2012 | 24.6°C | 18.3°C | 11.9°C | 32.9°C | 2.5°C | 56 mm | 68% | 2.6 m/s | 4.8 |
| 2011 | 22.1°C | 16.9°C | 11.7°C | 34.4°C | 3.4°C | 98 mm | 74% | 2.7 m/s | 4.2 |
| 2010 | 24.0°C | 18.4°C | 12.8°C | 30.9°C | 8.5°C | 74 mm | 75% | 3 m/s | 4.4 |
| 2009 | 23.7°C | 18.3°C | 12.8°C | 28.0°C | 6.8°C | 32 mm | 79% | 2 m/s | 4.4 |
| 2008 🌧️ | 24.0°C | 18.6°C | 13.2°C | 34.4°C | 7.4°C | 275 mm | 81% | 2.2 m/s | 3.9 |
| 2007 | 25.4°C | 19.0°C | 12.7°C | 30.6°C | 2.4°C | 28 mm | 75% | 2.6 m/s | 5.2 |
| 2006 | 22.4°C | 16.8°C | 11.2°C | 28.9°C | 4.3°C | 120 mm | 78% | 2.6 m/s | 3.9 |
| 2005 🔥 | 28.5°C | 21.8°C | 15.2°C | 34.6°C | 4.9°C | 66 mm | 64% | 2.6 m/s | 4.4 |
| 2004 | 26.1°C | 19.6°C | 13.2°C | 30.0°C | 7.2°C | 18 mm | 70% | 2.4 m/s | 5.3 |
| 2003 | 24.7°C | 18.2°C | 11.6°C | 30.8°C | 3.4°C | 56 mm | 67% | 2.7 m/s | 4.5 |
| 2002 | 28.1°C | 20.8°C | 13.6°C | 34.7°C | 4.2°C | 45 mm | 64% | 2.3 m/s | 4.8 |
| 2001 | 23.4°C | 17.2°C | 11.1°C | 31.2°C | 2.8°C | 106 mm | 74% | 2.7 m/s | 4.6 |
| 2000 | 25.2°C | 18.7°C | 12.1°C | 36.1°C | 3.2°C | 98 mm | 66% | 3 m/s | 4.2 |
| 1999 | 26.0°C | 18.5°C | 11.0°C | 34.6°C | 3.7°C | 68 mm | 59% | 2.7 m/s | 4.9 |
| 1998 | 27.2°C | 20.5°C | 13.8°C | 33.9°C | 9.2°C | 62 mm | 69% | 2.4 m/s | 4.5 |
| 1997 | 24.9°C | 18.5°C | 12.2°C | 30.5°C | 6.1°C | 54 mm | 69% | 2.6 m/s | 4.4 |
| 1996 | 23.1°C | 17.4°C | 11.6°C | 29.5°C | 6.1°C | 72 mm | 74% | 2.3 m/s | 4.2 |
| 1995 | 23.4°C | 16.9°C | 10.4°C | 30.7°C | 1.7°C | 35 mm | 65% | 2.6 m/s | 4.4 |
| 1994 | 24.6°C | 18.6°C | 12.5°C | 32.1°C | 5.8°C | 55 mm | 71% | 2.3 m/s | 4.2 |
| 1993 ❄️ | 19.3°C | 14.6°C | 9.9°C | 24.1°C | 0.7°C | 152 mm | 83% | 2.7 m/s | 3.3 |
| 1992 | 22.6°C | 16.6°C | 10.6°C | 28.7°C | 0.7°C | 155 mm | 76% | 2.7 m/s | 4.1 |
| 1991 | 24.5°C | 18.1°C | 11.6°C | 32.7°C | 0.6°C | 71 mm | 65% | 2.6 m/s | 4.5 |
| 1990 | 24.2°C | 18.4°C | 12.6°C | 32.0°C | 3.0°C | 35 mm | 75% | 2.5 m/s | 4.4 |
| 1989 | 21.7°C | 16.0°C | 10.2°C | 28.7°C | 1.0°C | 120 mm | 78% | 2.3 m/s | 4.5 |
| 1988 | 27.4°C | 19.9°C | 12.5°C | 32.4°C | 6.4°C | 47 mm | 60% | 2.9 m/s | 4.3 |
| 1987 | 23.1°C | 17.6°C | 12.1°C | 28.4°C | 6.6°C | 59 mm | 78% | 2.3 m/s | 4 |
| 1986 | 25.4°C | 19.6°C | 13.9°C | 29.8°C | 5.3°C | 169 mm | 74% | 2.8 m/s | 3.5 |
| 1985 | 25.1°C | 19.1°C | 13.1°C | 33.6°C | 4.2°C | 58 mm | 68% | 3.3 m/s | 3.9 |
| 1984 | 24.4°C | 17.7°C | 10.9°C | 34.6°C | 0.3°C | 68 mm | 66% | 2.9 m/s | 3.8 |
| 1983 | 25.0°C | 18.3°C | 11.6°C | 33.9°C | 1.3°C | 95 mm | 68% | 2.7 m/s | — |
| 1982 | 24.3°C | 18.0°C | 11.6°C | 30.3°C | 4.0°C | 41 mm | 73% | 2.5 m/s | — |
| 1981 | 22.6°C | 16.9°C | 11.2°C | 28.0°C | 2.8°C | 77 mm | 77% | 2.7 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 24.9°C with lows near 12.6°C (mean 18.8°C), based on 45 years of NASA POWER data.
September averages 79 mm of rainfall in Plainfield, about average for rainfall. The wettest on record was 275 mm in 2008.
The hottest September reached 36.1°C in 2000. The coldest dipped to 0.3°C in 1984.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.4°C. Daytime highs moved from 24.3°C to 27.2°C and overnight lows from 11.7°C to 13.6°C over the same span.
September is one of the warmer months of the year in Plainfield and about average for rainfall, so plan for around 24.9°C daytime highs and 12.6°C at night.
Not quite — September is the 9th coolest month in Plainfield, averaging 18.8°C.
For September in Plainfield, pack light layers you can adjust through the day, with typical highs of 24.9°C and lows of 12.6°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 72% — moderately humid.
Average wind speed in September is 2.6 m/s. The windiest September on record averaged 3.3 m/s (1985).
The wettest September on record was 2008 with 275 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 Plainfield 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.
