September is one of the warmer months of the year in Morristown, with average highs near 26.8°C and lows around 14.2°C (mean 20.5°C). It is one of the drier months, averaging 92 mm of rainfall and 70% relative humidity across the period.
September is one of the warmer months of the year in Morristown. Across 45 years of records, the warmest September in Morristown was 2019 — when the month averaged 24.8°C — while the coldest was 2001 at 18.3°C. Typical September days reach 26.8°C with nights near 14.2°C. The long-term trend is warming, about 0.4°C per decade.
September is one of the drier months in Morristown, averaging 92 mm of rainfall. The wettest September on record was 2024 with 235 mm, while the driest was 2019 at 14 mm.
Relative humidity in Morristown during September averages 70%. The most humid September was 1989 at 84%, and the least humid was 1999 at 50%.
September receives about 4.6 kWh/m²/day of solar energy in Morristown. The sunniest Septembers were 2005 and 2019 at 5.5 kWh/m²/day, and the cloudiest was 2009 at 3.9.
Average wind speed in Morristown during September is 0.5 m/s. The windiest September was 1999 at 0.7 m/s, while the calmest was 2023 at 0.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 19.6°C | 20.5°C | 20.3°C | 21.4°C | 20.6°C | +1°C |
| Avg High | 26.0°C | 27.1°C | 26.8°C | 27.5°C | 26.6°C | +0.6°C |
| Avg Low | 13.3°C | 14.0°C | 13.9°C | 15.3°C | 14.6°C | +1.3°C |
| Avg Rain | 89 mm | 71 mm | 103 mm | 90 mm | 114 mm | +25 mm |
September temperatures in Morristown have risen by about 1.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 2.3°C (1983) to a record high of 36°C (1998).
Rainfall in September is one of the drier months, averaging 92 mm, with a wettest year of 235 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.3°C per decade while lows rose 0.5°C per decade, narrowing the gap between day and night.
One of the best times to visit Morristown
September is one of the best times to visit Morristown. Expect days averaging 26.8°C and nights around 14.2°C (mean 20.5°C) — warmer than Morristown's yearly average — with higher rainfall (92 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 | 20.8°C | 14.9°C | 29.9°C | 9.3°C | 103 mm | 71% | 0.5 m/s | 4.8 |
| 2024 🌧️ | 27.6°C | 21.6°C | 15.7°C | 32.5°C | 7.9°C | 235 mm | 70% | 0.6 m/s | 4.4 |
| 2023 | 27.6°C | 21.4°C | 15.2°C | 31.4°C | 10.8°C | 48 mm | 71% | 0.4 m/s | 5 |
| 2022 | 26.3°C | 19.8°C | 13.3°C | 33.0°C | 3.8°C | 92 mm | 70% | 0.6 m/s | 4.8 |
| 2021 | 25.7°C | 19.9°C | 14.1°C | 29.7°C | 7.7°C | 71 mm | 75% | 0.5 m/s | 4.8 |
| 2020 | 25.5°C | 19.8°C | 14.2°C | 30.2°C | 5.6°C | 138 mm | 78% | 0.5 m/s | 4.5 |
| 2019 🔥 | 31.8°C | 24.8°C | 17.9°C | 35.9°C | 13.6°C | 14 mm | 60% | 0.5 m/s | 5.5 |
| 2018 | 28.6°C | 23.6°C | 18.5°C | 32.2°C | 13.4°C | 137 mm | 78% | 0.5 m/s | 4.2 |
| 2017 | 26.4°C | 20.1°C | 13.7°C | 30.8°C | 7.7°C | 57 mm | 69% | 0.6 m/s | 4.7 |
| 2016 | 30.1°C | 23.4°C | 16.8°C | 33.8°C | 9.8°C | 38 mm | 61% | 0.5 m/s | 5.3 |
| 2015 | 27.7°C | 21.5°C | 15.2°C | 32.6°C | 7.7°C | 92 mm | 69% | 0.5 m/s | 4.8 |
| 2014 | 26.9°C | 21.0°C | 15.1°C | 31.6°C | 6.5°C | 71 mm | 75% | 0.5 m/s | 4.6 |
| 2013 | 25.3°C | 19.4°C | 13.5°C | 30.0°C | 6.8°C | 88 mm | 77% | 0.5 m/s | 4.8 |
| 2012 | 25.5°C | 19.4°C | 13.3°C | 33.0°C | 3.0°C | 137 mm | 73% | 0.5 m/s | 4.5 |
| 2011 | 25.2°C | 19.7°C | 14.3°C | 35.5°C | 7.8°C | 152 mm | 75% | 0.5 m/s | 4.1 |
| 2010 | 27.8°C | 21.3°C | 14.8°C | 33.3°C | 9.3°C | 119 mm | 66% | 0.6 m/s | 5.2 |
| 2009 | 24.8°C | 19.8°C | 14.9°C | 29.0°C | 6.3°C | 168 mm | 79% | 0.5 m/s | 3.9 |
| 2008 | 27.5°C | 20.9°C | 14.3°C | 32.1°C | 6.6°C | 43 mm | 69% | 0.5 m/s | 4.9 |
| 2007 | 29.6°C | 22.4°C | 15.2°C | 33.7°C | 7.3°C | 45 mm | 59% | 0.5 m/s | 5.2 |
| 2006 | 24.3°C | 18.5°C | 12.6°C | 29.4°C | 5.6°C | 134 mm | 76% | 0.5 m/s | 4.1 |
| 2005 | 29.9°C | 22.4°C | 15.0°C | 33.4°C | 8.4°C | 30 mm | 60% | 0.6 m/s | 5.5 |
| 2004 | 25.6°C | 19.6°C | 13.7°C | 30.8°C | 6.8°C | 200 mm | 78% | 0.6 m/s | 4.5 |
| 2003 | 25.3°C | 19.0°C | 12.8°C | 30.2°C | 4.7°C | 101 mm | 73% | 0.6 m/s | 4.8 |
| 2002 | 28.8°C | 22.2°C | 15.6°C | 34.2°C | 11.3°C | 141 mm | 69% | 0.5 m/s | 4.4 |
| 2001 ❄️ | 24.8°C | 18.3°C | 11.8°C | 30.5°C | 3.2°C | 82 mm | 67% | 0.5 m/s | 4.9 |
| 2000 | 27.0°C | 20.2°C | 13.4°C | 31.9°C | 4.3°C | 81 mm | 68% | 0.6 m/s | 4.4 |
| 1999 | 28.1°C | 20.4°C | 12.8°C | 33.3°C | 5.2°C | 47 mm | 50% | 0.7 m/s | 5.1 |
| 1998 | 31.0°C | 23.6°C | 16.3°C | 36.0°C | 8.1°C | 32 mm | 56% | 0.5 m/s | 5.3 |
| 1997 | 27.6°C | 20.7°C | 13.8°C | 33.4°C | 7.7°C | 92 mm | 64% | 0.6 m/s | 4.6 |
| 1996 | 25.2°C | 19.2°C | 13.2°C | 29.7°C | 6.7°C | 99 mm | 72% | 0.6 m/s | 4.2 |
| 1995 | 26.7°C | 20.1°C | 13.6°C | 31.5°C | 7.7°C | 71 mm | 70% | 0.5 m/s | 4.2 |
| 1994 | 25.5°C | 19.1°C | 12.6°C | 31.3°C | 7.0°C | 56 mm | 71% | 0.5 m/s | 4.8 |
| 1993 | 27.3°C | 20.6°C | 13.9°C | 33.9°C | 2.3°C | 95 mm | 67% | 0.6 m/s | 4.3 |
| 1992 | 26.5°C | 20.4°C | 14.4°C | 30.7°C | 2.9°C | 72 mm | 75% | 0.5 m/s | 4.2 |
| 1991 | 25.8°C | 20.1°C | 14.4°C | 32.5°C | 3.8°C | 72 mm | 72% | 0.5 m/s | 4.3 |
| 1990 | 27.4°C | 21.0°C | 14.5°C | 33.8°C | 4.0°C | 79 mm | 66% | 0.6 m/s | 4.7 |
| 1989 | 23.8°C | 18.7°C | 13.7°C | 28.5°C | 3.8°C | 223 mm | 84% | 0.5 m/s | 4.1 |
| 1988 | 26.6°C | 20.2°C | 13.8°C | 31.1°C | 6.6°C | 103 mm | 74% | 0.5 m/s | 4 |
| 1987 | 26.1°C | 20.2°C | 14.3°C | 30.7°C | 8.7°C | 111 mm | 69% | 0.6 m/s | 4.1 |
| 1986 | 26.7°C | 21.0°C | 15.3°C | 30.3°C | 10.5°C | 82 mm | 76% | 0.5 m/s | 4.2 |
| 1985 | 26.9°C | 19.6°C | 12.3°C | 31.6°C | 5.5°C | 27 mm | 64% | 0.5 m/s | 5 |
| 1984 | 26.3°C | 19.1°C | 11.9°C | 32.0°C | 5.5°C | 28 mm | 62% | 0.6 m/s | 4.7 |
| 1983 | 26.5°C | 19.9°C | 13.3°C | 33.3°C | 2.3°C | 58 mm | 65% | 0.6 m/s | — |
| 1982 | 24.7°C | 18.7°C | 12.7°C | 29.0°C | 6.0°C | 69 mm | 74% | 0.5 m/s | — |
| 1981 | 26.2°C | 19.2°C | 12.3°C | 32.6°C | 5.4°C | 100 mm | 64% | 0.6 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 26.8°C with lows near 14.2°C (mean 20.5°C), based on 45 years of NASA POWER data.
September averages 92 mm of rainfall in Morristown, one of the drier months. The wettest on record was 235 mm in 2024.
The hottest September reached 36°C in 1998. The coldest dipped to 2.3°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.4°C. Daytime highs moved from 26.1°C to 26.8°C and overnight lows from 12.5°C to 14.6°C over the same span.
September is one of the warmer months of the year in Morristown and one of the drier months, so plan for around 26.8°C daytime highs and 14.2°C at night.
Not quite — September is the 9th coolest month in Morristown, averaging 20.5°C.
For September in Morristown, pack light layers you can adjust through the day, with typical highs of 26.8°C and lows of 14.2°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 70% — moderately humid.
Average wind speed in September is 0.5 m/s. The windiest September on record averaged 0.7 m/s (1999).
The wettest September on record was 2024 with 235 mm. On average, September sees 92 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 Morristown 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.
