September is one of the warmer months of the year in Harrisburg, with average highs near 25°C and lows around 12.7°C (mean 18.9°C). It is a relatively wet time of year, averaging 110 mm of rainfall and 71% relative humidity across the period.
September is one of the warmer months of the year in Harrisburg. Across 45 years of records, the warmest September in Harrisburg was 2019 — when the month averaged 21.4°C — while the coldest was 2006 at 16.7°C. Typical September days reach 25°C with nights near 12.7°C. The long-term trend is warming, about 0.5°C per decade.
September is a relatively wet time of year in Harrisburg, averaging 110 mm of rainfall. The wettest September on record was 2011 with 374 mm, while the driest was 2005 at 25 mm.
Relative humidity in Harrisburg during September averages 71%. The most humid Septembers were 2011 and 2018 at 88%, and the least humid was 1983 at 58%.
September receives about 4.2 kWh/m²/day of solar energy in Harrisburg. The sunniest September was 2007 at 5.1 kWh/m²/day, and the cloudiest were 2011 and 2018 at 3.1.
Average wind speed in Harrisburg during September is 0.4 m/s. The windiest Septembers were 2003, 2010 and 2016, among others at 0.5 m/s, while the calmest were 2023, 2024 and 2025, among others at 0.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 18.3°C | 18.1°C | 18.7°C | 19.8°C | 19.6°C | +1.3°C |
| Avg High | 24.7°C | 24.2°C | 24.8°C | 25.9°C | 25.7°C | +1°C |
| Avg Low | 11.8°C | 11.9°C | 12.6°C | 13.7°C | 13.6°C | +1.8°C |
| Avg Rain | 84 mm | 114 mm | 118 mm | 126 mm | 106 mm | +22 mm |
September temperatures in Harrisburg have risen by about 1.3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 0.8°C (2000) to a record high of 36.2°C (2023).
Rainfall in September is a relatively wet time of year, averaging 110 mm, with a wettest year of 374 mm.
One of the best times to visit Harrisburg
September is one of the best times to visit Harrisburg. Expect days averaging 25°C and nights around 12.7°C (mean 18.9°C) — warmer than Harrisburg's yearly average — with higher rainfall (110 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 | 27.9°C | 21.1°C | 14.2°C | 32.2°C | 8.4°C | 48 mm | 61% | 0.4 m/s | 4.5 |
| 2024 | 25.8°C | 19.9°C | 14.0°C | 30.9°C | 7.8°C | 67 mm | 72% | 0.4 m/s | 4.1 |
| 2023 | 25.8°C | 19.8°C | 13.7°C | 36.2°C | 7.4°C | 112 mm | 73% | 0.4 m/s | 4.2 |
| 2022 | 24.8°C | 19.1°C | 13.4°C | 31.7°C | 6.0°C | 108 mm | 74% | 0.4 m/s | 4.2 |
| 2021 | 24.1°C | 18.8°C | 13.5°C | 28.8°C | 7.9°C | 247 mm | 83% | 0.4 m/s | 4.3 |
| 2020 | 25.7°C | 19.1°C | 12.5°C | 31.1°C | 2.9°C | 55 mm | 67% | 0.4 m/s | 4.1 |
| 2019 🔥 | 28.1°C | 21.4°C | 14.6°C | 35.0°C | 7.7°C | 27 mm | 65% | 0.4 m/s | 4.3 |
| 2018 | 24.5°C | 20.2°C | 15.9°C | 32.0°C | 8.1°C | 232 mm | 88% | 0.4 m/s | 3.1 |
| 2017 | 25.9°C | 19.7°C | 13.5°C | 34.0°C | 6.8°C | 50 mm | 70% | 0.4 m/s | 4.3 |
| 2016 | 28.0°C | 21.3°C | 14.6°C | 34.2°C | 7.4°C | 86 mm | 64% | 0.5 m/s | 4.6 |
| 2015 | 27.3°C | 20.8°C | 14.3°C | 35.0°C | 9.1°C | 97 mm | 67% | 0.4 m/s | 4.6 |
| 2014 | 25.9°C | 19.3°C | 12.6°C | 32.8°C | 6.1°C | 43 mm | 67% | 0.4 m/s | 4.4 |
| 2013 | 25.3°C | 18.2°C | 11.1°C | 34.2°C | 3.6°C | 44 mm | 64% | 0.4 m/s | 4.8 |
| 2012 | 24.3°C | 18.4°C | 12.6°C | 33.4°C | 4.4°C | 135 mm | 73% | 0.4 m/s | 4.2 |
| 2011 🌧️ | 23.3°C | 18.8°C | 14.3°C | 30.1°C | 4.5°C | 374 mm | 88% | 0.4 m/s | 3.1 |
| 2010 | 26.7°C | 20.1°C | 13.4°C | 35.8°C | 7.6°C | 167 mm | 63% | 0.5 m/s | 4.6 |
| 2009 | 22.7°C | 17.5°C | 12.2°C | 27.8°C | 6.3°C | 85 mm | 76% | 0.4 m/s | 4 |
| 2008 | 25.1°C | 19.1°C | 13.1°C | 34.0°C | 7.2°C | 158 mm | 73% | 0.4 m/s | 4.3 |
| 2007 | 26.9°C | 20.0°C | 13.2°C | 33.2°C | 5.2°C | 42 mm | 67% | 0.4 m/s | 5.1 |
| 2006 ❄️ | 21.8°C | 16.7°C | 11.7°C | 26.9°C | 4.5°C | 127 mm | 82% | 0.4 m/s | 3.4 |
| 2005 | 28.3°C | 21.2°C | 14.1°C | 33.5°C | 5.4°C | 25 mm | 60% | 0.4 m/s | 4.9 |
| 2004 | 24.6°C | 19.1°C | 13.5°C | 28.6°C | 5.7°C | 239 mm | 81% | 0.4 m/s | 4 |
| 2003 | 23.1°C | 17.9°C | 12.8°C | 26.8°C | 5.5°C | 185 mm | 83% | 0.5 m/s | 3.7 |
| 2002 | 27.2°C | 20.4°C | 13.7°C | 35.7°C | 6.6°C | 122 mm | 63% | 0.5 m/s | 4.3 |
| 2001 | 24.6°C | 17.7°C | 10.7°C | 31.1°C | 4.4°C | 93 mm | 64% | 0.5 m/s | 4.6 |
| 2000 | 23.4°C | 17.0°C | 10.6°C | 31.2°C | 0.8°C | 107 mm | 72% | 0.4 m/s | 4.2 |
| 1999 | 23.8°C | 18.1°C | 12.4°C | 31.9°C | 4.6°C | 241 mm | 76% | 0.5 m/s | 4 |
| 1998 | 27.6°C | 20.4°C | 13.3°C | 34.3°C | 4.4°C | 57 mm | 63% | 0.4 m/s | 4.5 |
| 1997 | 23.5°C | 17.4°C | 11.3°C | 31.4°C | 3.9°C | 95 mm | 70% | 0.5 m/s | 4.3 |
| 1996 | 23.3°C | 18.0°C | 12.8°C | 31.2°C | 6.4°C | 173 mm | 80% | 0.5 m/s | 3.7 |
| 1995 | 25.2°C | 18.3°C | 11.5°C | 32.5°C | 3.1°C | 58 mm | 60% | 0.4 m/s | 4.2 |
| 1994 | 22.8°C | 16.9°C | 11.0°C | 29.4°C | 5.6°C | 95 mm | 76% | 0.4 m/s | 4.2 |
| 1993 | 23.6°C | 18.1°C | 12.5°C | 31.5°C | 3.5°C | 157 mm | 75% | 0.4 m/s | 3.4 |
| 1992 | 23.8°C | 17.7°C | 11.5°C | 30.1°C | 2.9°C | 117 mm | 74% | 0.5 m/s | 3.8 |
| 1991 | 24.9°C | 18.2°C | 11.4°C | 34.4°C | 1.9°C | 77 mm | 65% | 0.4 m/s | 4.2 |
| 1990 | 23.9°C | 17.6°C | 11.4°C | 30.8°C | 2.0°C | 71 mm | 74% | 0.4 m/s | 4.1 |
| 1989 | 24.9°C | 19.0°C | 13.0°C | 34.1°C | 2.4°C | 84 mm | 71% | 0.4 m/s | 3.8 |
| 1988 | 23.6°C | 17.0°C | 10.4°C | 28.8°C | 5.3°C | 83 mm | 72% | 0.4 m/s | 4.2 |
| 1987 | 23.0°C | 17.7°C | 12.5°C | 27.3°C | 5.0°C | 194 mm | 82% | 0.4 m/s | 3.8 |
| 1986 | 24.9°C | 18.6°C | 12.3°C | 31.1°C | 3.5°C | 62 mm | 71% | 0.4 m/s | 3.8 |
| 1985 | 26.5°C | 19.5°C | 12.6°C | 34.6°C | 4.9°C | 102 mm | 64% | 0.4 m/s | 4.4 |
| 1984 | 23.7°C | 16.8°C | 9.9°C | 31.1°C | 3.9°C | 33 mm | 69% | 0.4 m/s | 4.6 |
| 1983 | 26.8°C | 19.4°C | 12.0°C | 35.3°C | 3.3°C | 45 mm | 58% | 0.5 m/s | — |
| 1982 | 25.2°C | 18.7°C | 12.2°C | 31.1°C | 6.7°C | 78 mm | 67% | 0.4 m/s | — |
| 1981 | 23.7°C | 17.6°C | 11.5°C | 31.4°C | 3.9°C | 72 mm | 71% | 0.5 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 25°C with lows near 12.7°C (mean 18.9°C), based on 45 years of NASA POWER data.
September averages 110 mm of rainfall in Harrisburg, a relatively wet time of year. The wettest on record was 374 mm in 2011.
The hottest September reached 36.2°C in 2023. The coldest dipped to 0.8°C in 2000.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.3°C. Daytime highs moved from 25.2°C to 25.7°C and overnight lows from 11.6°C to 13.8°C over the same span.
September is one of the warmer months of the year in Harrisburg and a relatively wet time of year, so plan for around 25°C daytime highs and 12.7°C at night.
Not quite — September is the 9th coolest month in Harrisburg, averaging 18.9°C.
For September in Harrisburg, pack light layers you can adjust through the day, with typical highs of 25°C and lows of 12.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 71% — moderately humid.
Average wind speed in September is 0.4 m/s. The windiest September on record averaged 0.5 m/s (1981).
The wettest September on record was 2011 with 374 mm. On average, September sees 110 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 Harrisburg 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.
