September is one of the warmer months of the year in Fort Smith, with average highs near 30.1°C and lows around 17.1°C (mean 23.6°C). It is about average for rainfall, averaging 104 mm of rainfall and 66% relative humidity across the period.
September is one of the warmer months of the year in Fort Smith. Across 45 years of records, the warmest September in Fort Smith was 1998 — when the month averaged 27°C — while the coldest was 2009 at 21.1°C. Typical September days reach 30.1°C with nights near 17.1°C. The long-term trend is warming, about 0.4°C per decade.
September is about average for rainfall in Fort Smith, averaging 104 mm of rainfall. The wettest September on record was 2009 with 233 mm, while the driest was 2017 at 7 mm.
Relative humidity in Fort Smith during September averages 66%. The most humid September was 2020 at 82%, and the least humid was 2000 at 46%.
September receives about 4.9 kWh/m²/day of solar energy in Fort Smith. The sunniest September was 2021 at 5.6 kWh/m²/day, and the cloudiest were 1986 and 2009 at 4.
Average wind speed in Fort Smith during September is 1.5 m/s. The windiest September was 1985 at 1.9 m/s, while the calmest was 2025 at 1.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 23.2°C | 23.0°C | 23.3°C | 24.4°C | 24.6°C | +1.4°C |
| Avg High | 29.8°C | 29.4°C | 29.9°C | 30.7°C | 31.2°C | +1.4°C |
| Avg Low | 16.5°C | 16.6°C | 16.8°C | 18.0°C | 17.9°C | +1.4°C |
| Avg Rain | 99 mm | 136 mm | 107 mm | 87 mm | 80 mm | -20 mm |
September temperatures in Fort Smith have risen by about 1.8°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 2.8°C (1984) to a record high of 43.5°C (2000).
Rainfall in September is about average for rainfall, averaging 104 mm, with a wettest year of 233 mm.
One of the best times to visit Fort Smith
September is one of the best times to visit Fort Smith. Expect days averaging 30.1°C and nights around 17.1°C (mean 23.6°C) — warmer than Fort Smith's yearly average — with higher rainfall (104 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 | 30.5°C | 24.4°C | 18.3°C | 35.7°C | 12.0°C | 125 mm | 67% | 1.1 m/s | 5 |
| 2024 | 31.6°C | 24.5°C | 17.4°C | 37.5°C | 10.3°C | 38 mm | 63% | 1.5 m/s | 5 |
| 2023 | 32.8°C | 25.8°C | 18.8°C | 39.0°C | 14.4°C | 105 mm | 60% | 1.4 m/s | 5.1 |
| 2022 | 32.7°C | 25.3°C | 17.9°C | 37.6°C | 9.7°C | 29 mm | 57% | 1.4 m/s | 5.5 |
| 2021 | 33.2°C | 25.9°C | 18.6°C | 37.6°C | 11.6°C | 47 mm | 59% | 1.5 m/s | 5.6 |
| 2020 | 26.6°C | 21.5°C | 16.4°C | 31.0°C | 7.8°C | 134 mm | 82% | 1.4 m/s | 4.6 |
| 2019 | 32.2°C | 26.8°C | 21.5°C | 36.0°C | 20.0°C | 98 mm | 73% | 1.4 m/s | 5.1 |
| 2018 | 29.1°C | 23.8°C | 18.6°C | 35.8°C | 10.4°C | 101 mm | 78% | 1.4 m/s | 4.4 |
| 2017 | 30.8°C | 24.1°C | 17.3°C | 35.1°C | 11.1°C | 7 mm | 63% | 1.4 m/s | 5.3 |
| 2016 | 32.0°C | 25.3°C | 18.5°C | 35.9°C | 10.6°C | 53 mm | 67% | 1.5 m/s | 5.5 |
| 2015 | 31.4°C | 24.9°C | 18.4°C | 36.0°C | 11.6°C | 62 mm | 66% | 1.4 m/s | 5.2 |
| 2014 | 29.2°C | 23.5°C | 17.7°C | 36.1°C | 10.5°C | 111 mm | 72% | 1.4 m/s | 4.7 |
| 2013 | 32.9°C | 25.4°C | 17.8°C | 37.7°C | 10.1°C | 60 mm | 60% | 1.5 m/s | 5.4 |
| 2012 | 31.5°C | 24.7°C | 17.9°C | 40.9°C | 10.5°C | 92 mm | 64% | 1.5 m/s | 4.8 |
| 2011 | 29.5°C | 22.2°C | 14.9°C | 40.0°C | 9.0°C | 70 mm | 56% | 1.7 m/s | 5.2 |
| 2010 | 28.8°C | 23.1°C | 17.5°C | 34.9°C | 8.6°C | 221 mm | 76% | 1.6 m/s | 4.9 |
| 2009 ❄️ 🌧️ | 25.9°C | 21.1°C | 16.3°C | 31.4°C | 7.4°C | 233 mm | 81% | 1.6 m/s | 4 |
| 2008 | 26.7°C | 21.4°C | 16.1°C | 33.1°C | 8.4°C | 178 mm | 80% | 1.7 m/s | 4.9 |
| 2007 | 29.4°C | 23.7°C | 17.9°C | 34.8°C | 12.3°C | 137 mm | 74% | 1.5 m/s | 4.8 |
| 2006 | 28.5°C | 21.6°C | 14.7°C | 34.9°C | 7.2°C | 113 mm | 65% | 1.7 m/s | 5 |
| 2005 | 33.3°C | 26.5°C | 19.7°C | 36.7°C | 10.3°C | 83 mm | 62% | 1.6 m/s | 5.2 |
| 2004 | 31.6°C | 24.0°C | 16.5°C | 35.8°C | 12.1°C | 28 mm | 58% | 1.5 m/s | 5.5 |
| 2003 | 28.2°C | 21.9°C | 15.5°C | 32.7°C | 7.3°C | 88 mm | 69% | 1.6 m/s | 4.9 |
| 2002 | 32.6°C | 25.1°C | 17.6°C | 36.9°C | 9.9°C | 28 mm | 58% | 1.6 m/s | 5.2 |
| 2001 | 29.2°C | 22.4°C | 15.7°C | 35.9°C | 6.3°C | 108 mm | 65% | 1.4 m/s | 4.9 |
| 2000 | 33.5°C | 25.5°C | 17.5°C | 43.5°C | 4.7°C | 71 mm | 46% | 1.7 m/s | 5.2 |
| 1999 | 29.7°C | 22.6°C | 15.5°C | 36.7°C | 6.6°C | 98 mm | 58% | 1.6 m/s | 4.9 |
| 1998 🔥 | 33.1°C | 27.0°C | 20.9°C | 42.8°C | 15.3°C | 165 mm | 62% | 1.6 m/s | 5.1 |
| 1997 | 30.7°C | 23.8°C | 17.0°C | 35.8°C | 11.3°C | 72 mm | 64% | 1.5 m/s | 4.9 |
| 1996 | 28.1°C | 21.8°C | 15.4°C | 34.1°C | 5.4°C | 180 mm | 68% | 1.4 m/s | 4.5 |
| 1995 | 29.0°C | 22.5°C | 16.1°C | 39.5°C | 3.8°C | 128 mm | 62% | 1.6 m/s | 4.1 |
| 1994 | 29.6°C | 22.4°C | 15.3°C | 35.0°C | 7.4°C | 43 mm | 65% | 1.5 m/s | 5 |
| 1993 | 27.8°C | 21.3°C | 14.7°C | 33.6°C | 6.7°C | 209 mm | 72% | 1.6 m/s | 4.8 |
| 1992 | 27.6°C | 21.5°C | 15.4°C | 32.8°C | 5.5°C | 185 mm | 75% | 1.5 m/s | 4.6 |
| 1991 | 26.9°C | 21.6°C | 16.4°C | 34.0°C | 6.3°C | 135 mm | 75% | 1.4 m/s | 4.4 |
| 1990 | 31.1°C | 25.0°C | 19.0°C | 39.9°C | 7.1°C | 144 mm | 66% | 1.3 m/s | 4.7 |
| 1989 | 27.4°C | 21.2°C | 14.9°C | 36.8°C | 3.0°C | 116 mm | 70% | 1.5 m/s | 4.3 |
| 1988 | 31.1°C | 23.9°C | 16.8°C | 36.2°C | 11.1°C | 110 mm | 64% | 1.4 m/s | 4.7 |
| 1987 | 29.4°C | 22.9°C | 16.4°C | 34.5°C | 8.9°C | 103 mm | 66% | 1.3 m/s | 4.7 |
| 1986 | 29.0°C | 23.9°C | 18.8°C | 31.7°C | 12.7°C | 202 mm | 77% | 1.6 m/s | 4 |
| 1985 | 29.6°C | 23.1°C | 16.6°C | 40.2°C | 5.7°C | 102 mm | 63% | 1.9 m/s | 4.7 |
| 1984 | 29.3°C | 22.5°C | 15.7°C | 37.1°C | 2.8°C | 138 mm | 63% | 1.8 m/s | 4.7 |
| 1983 | 31.8°C | 24.4°C | 16.9°C | 38.0°C | 4.9°C | 40 mm | 54% | 1.6 m/s | — |
| 1982 | 30.9°C | 23.6°C | 16.3°C | 36.7°C | 6.3°C | 33 mm | 58% | 1.6 m/s | — |
| 1981 | 30.1°C | 23.3°C | 16.5°C | 34.1°C | 6.3°C | 52 mm | 65% | 1.4 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 30.1°C with lows near 17.1°C (mean 23.6°C), based on 45 years of NASA POWER data.
September averages 104 mm of rainfall in Fort Smith, about average for rainfall. The wettest on record was 233 mm in 2009.
The hottest September reached 43.5°C in 2000. The coldest dipped to 2.8°C in 1984.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.8°C. Daytime highs moved from 30.3°C to 32.2°C and overnight lows from 16.4°C to 18.2°C over the same span.
September is one of the warmer months of the year in Fort Smith and about average for rainfall, so plan for around 30.1°C daytime highs and 17.1°C at night.
Not quite — September is the 9th coolest month in Fort Smith, averaging 23.6°C.
For September in Fort Smith, pack light, breathable clothing and sun protection, with typical highs of 30.1°C and lows of 17.1°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 66% — moderately humid.
Average wind speed in September is 1.5 m/s. The windiest September on record averaged 1.9 m/s (1985).
The wettest September on record was 2009 with 233 mm. On average, September sees 104 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 Fort Smith 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.
