September is one of the warmer months of the year in Chambersburg, with average highs near 25.1°C and lows around 12.8°C (mean 19°C). It is a relatively wet time of year, averaging 105 mm of rainfall and 70% relative humidity across the period.
September is one of the warmer months of the year in Chambersburg. Across 45 years of records, the warmest September in Chambersburg was 2019 — when the month averaged 21.9°C — while the coldest was 1984 at 16.9°C. Typical September days reach 25.1°C with nights near 12.8°C. The long-term trend is warming, about 0.5°C per decade.
September is a relatively wet time of year in Chambersburg, averaging 105 mm of rainfall. The wettest September on record was 2011 with 307 mm, while the driest was 2005 at 13 mm.
Relative humidity in Chambersburg during September averages 70%. The most humid September was 2018 at 88%, and the least humid was 1983 at 57%.
September receives about 4.2 kWh/m²/day of solar energy in Chambersburg. The sunniest September was 2007 at 5.3 kWh/m²/day, and the cloudiest were 2011 and 2018 at 3.2.
Average wind speed in Chambersburg during September is 0.9 m/s. The windiest Septembers were 1996 and 1999 at 1 m/s, while the calmest were 2023, 2024 and 2025, among others at 0.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 18.5°C | 18.3°C | 18.8°C | 19.9°C | 19.6°C | +1.1°C |
| Avg High | 25.0°C | 24.5°C | 24.9°C | 25.9°C | 25.6°C | +0.6°C |
| Avg Low | 12.0°C | 12.1°C | 12.7°C | 13.8°C | 13.6°C | +1.6°C |
| Avg Rain | 70 mm | 111 mm | 113 mm | 123 mm | 106 mm | +36 mm |
September temperatures in Chambersburg have risen by about 1.2°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 1.7°C (2000) to a record high of 37°C (2023).
Rainfall in September is a relatively wet time of year, averaging 105 mm, with a wettest year of 307 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.3°C per decade while lows rose 0.6°C per decade, narrowing the gap between day and night.
One of the best times to visit Chambersburg
September is one of the best times to visit Chambersburg. Expect days averaging 25.1°C and nights around 12.8°C (mean 19°C) — warmer than Chambersburg's yearly average — with higher rainfall (105 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 | 27.5°C | 20.9°C | 14.3°C | 32.4°C | 8.4°C | 41 mm | 61% | 0.8 m/s | 4.2 |
| 2024 | 25.2°C | 19.5°C | 13.9°C | 29.8°C | 7.3°C | 87 mm | 74% | 0.8 m/s | 4.1 |
| 2023 | 26.2°C | 20.0°C | 13.8°C | 37.0°C | 7.3°C | 116 mm | 70% | 0.8 m/s | 4.4 |
| 2022 | 25.3°C | 19.4°C | 13.5°C | 32.4°C | 6.8°C | 97 mm | 72% | 0.8 m/s | 4.4 |
| 2021 | 24.3°C | 18.9°C | 13.4°C | 29.1°C | 8.0°C | 240 mm | 81% | 0.9 m/s | 4.5 |
| 2020 | 25.3°C | 18.9°C | 12.5°C | 30.3°C | 2.8°C | 56 mm | 68% | 0.8 m/s | 4.2 |
| 2019 🔥 | 28.7°C | 21.9°C | 15.1°C | 35.5°C | 7.8°C | 25 mm | 64% | 0.8 m/s | 4.5 |
| 2018 | 24.3°C | 20.2°C | 16.2°C | 32.2°C | 8.4°C | 300 mm | 88% | 0.8 m/s | 3.2 |
| 2017 | 25.8°C | 19.5°C | 13.2°C | 32.9°C | 7.0°C | 45 mm | 70% | 0.8 m/s | 4.5 |
| 2016 | 27.8°C | 21.4°C | 15.0°C | 34.6°C | 8.3°C | 97 mm | 65% | 0.9 m/s | 4.3 |
| 2015 | 26.9°C | 20.6°C | 14.3°C | 34.5°C | 8.3°C | 88 mm | 67% | 0.8 m/s | 4.4 |
| 2014 | 25.6°C | 19.1°C | 12.7°C | 31.9°C | 5.7°C | 42 mm | 68% | 0.8 m/s | 4.4 |
| 2013 | 25.3°C | 18.4°C | 11.6°C | 34.1°C | 3.8°C | 37 mm | 64% | 0.8 m/s | 4.9 |
| 2012 | 24.3°C | 18.4°C | 12.6°C | 32.3°C | 4.5°C | 129 mm | 73% | 0.8 m/s | 4.4 |
| 2011 🌧️ | 23.2°C | 18.7°C | 14.2°C | 31.8°C | 4.0°C | 307 mm | 87% | 0.8 m/s | 3.2 |
| 2010 | 27.3°C | 20.3°C | 13.4°C | 35.9°C | 8.3°C | 159 mm | 62% | 0.9 m/s | 4.7 |
| 2009 | 23.4°C | 18.0°C | 12.6°C | 29.2°C | 6.8°C | 74 mm | 74% | 0.9 m/s | 4 |
| 2008 | 24.9°C | 19.1°C | 13.2°C | 33.0°C | 7.7°C | 152 mm | 74% | 0.8 m/s | 4.3 |
| 2007 | 26.8°C | 20.0°C | 13.1°C | 33.3°C | 5.0°C | 37 mm | 67% | 0.8 m/s | 5.3 |
| 2006 | 22.5°C | 17.2°C | 11.9°C | 27.7°C | 5.1°C | 130 mm | 79% | 0.9 m/s | 3.5 |
| 2005 | 28.2°C | 21.2°C | 14.2°C | 32.6°C | 5.2°C | 13 mm | 61% | 0.8 m/s | 4.9 |
| 2004 | 24.5°C | 19.2°C | 13.8°C | 28.9°C | 5.9°C | 247 mm | 80% | 0.9 m/s | 3.9 |
| 2003 | 23.2°C | 18.1°C | 13.0°C | 28.7°C | 4.8°C | 197 mm | 83% | 0.9 m/s | 3.9 |
| 2002 | 27.0°C | 20.4°C | 13.7°C | 34.8°C | 7.7°C | 108 mm | 65% | 0.9 m/s | 4.4 |
| 2001 | 25.1°C | 17.9°C | 10.7°C | 31.7°C | 4.4°C | 66 mm | 61% | 0.9 m/s | 4.8 |
| 2000 | 23.4°C | 17.1°C | 10.8°C | 30.7°C | 1.7°C | 109 mm | 72% | 0.9 m/s | 4.3 |
| 1999 | 24.2°C | 18.3°C | 12.4°C | 31.5°C | 4.7°C | 195 mm | 73% | 1 m/s | 4.1 |
| 1998 | 28.2°C | 20.9°C | 13.7°C | 34.7°C | 4.8°C | 46 mm | 61% | 0.8 m/s | 4.8 |
| 1997 | 24.0°C | 17.7°C | 11.5°C | 32.3°C | 4.1°C | 110 mm | 68% | 0.9 m/s | 4.4 |
| 1996 | 22.5°C | 17.5°C | 12.6°C | 29.8°C | 6.7°C | 232 mm | 82% | 1 m/s | 3.8 |
| 1995 | 25.1°C | 18.5°C | 11.8°C | 32.0°C | 3.8°C | 52 mm | 61% | 0.8 m/s | 4.2 |
| 1994 | 23.2°C | 17.2°C | 11.3°C | 29.9°C | 5.2°C | 81 mm | 74% | 0.9 m/s | 4.4 |
| 1993 | 24.2°C | 18.5°C | 12.7°C | 32.4°C | 3.6°C | 150 mm | 73% | 0.9 m/s | 3.5 |
| 1992 | 23.8°C | 17.9°C | 11.9°C | 29.7°C | 2.9°C | 108 mm | 73% | 0.9 m/s | 3.9 |
| 1991 | 25.3°C | 18.5°C | 11.7°C | 34.7°C | 1.8°C | 78 mm | 63% | 0.8 m/s | 4.3 |
| 1990 | 24.2°C | 17.9°C | 11.6°C | 31.7°C | 2.3°C | 60 mm | 72% | 0.9 m/s | 4.2 |
| 1989 | 24.9°C | 18.9°C | 13.0°C | 33.6°C | 3.5°C | 61 mm | 71% | 0.9 m/s | 3.6 |
| 1988 | 24.0°C | 17.4°C | 10.8°C | 29.4°C | 5.4°C | 84 mm | 70% | 0.8 m/s | 4.3 |
| 1987 | 23.6°C | 18.2°C | 12.9°C | 27.9°C | 5.2°C | 165 mm | 79% | 0.8 m/s | 4 |
| 1986 | 25.7°C | 19.3°C | 12.9°C | 32.0°C | 3.5°C | 42 mm | 69% | 0.9 m/s | 4 |
| 1985 | 26.7°C | 19.7°C | 12.6°C | 34.2°C | 5.4°C | 57 mm | 61% | 0.8 m/s | 4.7 |
| 1984 ❄️ | 23.8°C | 16.9°C | 10.1°C | 32.1°C | 3.8°C | 43 mm | 68% | 0.9 m/s | 4.5 |
| 1983 | 26.8°C | 19.5°C | 12.2°C | 35.5°C | 3.2°C | 45 mm | 57% | 0.9 m/s | — |
| 1982 | 25.4°C | 18.8°C | 12.3°C | 30.6°C | 6.7°C | 69 mm | 67% | 0.8 m/s | — |
| 1981 | 23.8°C | 17.7°C | 11.5°C | 31.3°C | 3.7°C | 65 mm | 70% | 0.9 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 25.1°C with lows near 12.8°C (mean 19°C), based on 45 years of NASA POWER data.
September averages 105 mm of rainfall in Chambersburg, a relatively wet time of year. The wettest on record was 307 mm in 2011.
The hottest September reached 37°C in 2023. The coldest dipped to 1.7°C in 2000.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.2°C. Daytime highs moved from 25.3°C to 25.7°C and overnight lows from 11.7°C to 13.8°C over the same span.
September is one of the warmer months of the year in Chambersburg and a relatively wet time of year, so plan for around 25.1°C daytime highs and 12.8°C at night.
Not quite — September is the 9th coolest month in Chambersburg, averaging 19°C.
For September in Chambersburg, pack light layers you can adjust through the day, with typical highs of 25.1°C and lows of 12.8°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 70% — moderately humid.
Average wind speed in September is 0.9 m/s. The windiest September on record averaged 1 m/s (1996).
The wettest September on record was 2011 with 307 mm. On average, September sees 105 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 Chambersburg 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.
