September is one of the warmer months of the year in Keller, with average highs near 32.3°C and lows around 19.5°C (mean 25.9°C). It is about average for rainfall, averaging 72 mm of rainfall and 61% relative humidity across the period.
September is one of the warmer months of the year in Keller. Across 45 years of records, the warmest September in Keller was 2019 — when the month averaged 30°C — while the coldest was 1991 at 22.7°C. Typical September days reach 32.3°C with nights near 19.5°C. The long-term trend is warming, about 0.4°C per decade.
September is about average for rainfall in Keller, averaging 72 mm of rainfall. The wettest September on record was 2010 with 215 mm, while the driest was 1983 at 11 mm.
Relative humidity in Keller during September averages 61%. The most humid September was 2018 at 80%, and the least humid was 2000 at 41%.
September receives about 5.3 kWh/m²/day of solar energy in Keller. The sunniest September was 2011 at 6 kWh/m²/day, and the cloudiest was 2018 at 4.3.
Average wind speed in Keller during September is 2.6 m/s. The windiest September was 1985 at 3.5 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 | 25.4°C | 25.6°C | 25.4°C | 26.8°C | 26.7°C | +1.3°C |
| Avg High | 32.0°C | 31.9°C | 31.9°C | 32.8°C | 33.3°C | +1.3°C |
| Avg Low | 18.8°C | 19.2°C | 19.0°C | 20.7°C | 20.2°C | +1.4°C |
| Avg Rain | 74 mm | 74 mm | 66 mm | 80 mm | 63 mm | -11 mm |
September temperatures in Keller have risen by about 1.5°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 4.4°C (1984) to a record high of 45.3°C (2000).
Rainfall in September is about average for rainfall, averaging 72 mm, with a wettest year of 215 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 Keller
September is one of the best times to visit Keller. Expect days averaging 32.3°C and nights around 19.5°C (mean 25.9°C) — warmer than Keller's yearly average — with moderate rainfall (72 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 | 34.0°C | 27.2°C | 20.4°C | 39.4°C | 15.9°C | 41 mm | 56% | 1.9 m/s | 5.7 |
| 2024 | 32.1°C | 25.8°C | 19.4°C | 37.7°C | 13.7°C | 109 mm | 64% | 2.1 m/s | 5.4 |
| 2023 | 35.9°C | 29.3°C | 22.7°C | 44.8°C | 18.5°C | 40 mm | 53% | 2.5 m/s | 5.4 |
| 2022 | 33.3°C | 26.7°C | 20.1°C | 37.1°C | 13.5°C | 29 mm | 59% | 2.1 m/s | 5.9 |
| 2021 | 34.8°C | 27.6°C | 20.5°C | 40.1°C | 13.2°C | 37 mm | 50% | 2.2 m/s | 5.7 |
| 2020 | 29.5°C | 23.7°C | 18.0°C | 35.0°C | 9.8°C | 124 mm | 74% | 2.5 m/s | 4.5 |
| 2019 🔥 | 36.2°C | 30.0°C | 23.8°C | 38.9°C | 21.9°C | 12 mm | 56% | 2.8 m/s | 5.7 |
| 2018 | 29.3°C | 25.1°C | 20.8°C | 36.1°C | 11.9°C | 189 mm | 80% | 2.1 m/s | 4.3 |
| 2017 | 32.6°C | 26.2°C | 19.8°C | 37.8°C | 13.8°C | 61 mm | 62% | 2.5 m/s | 5.5 |
| 2016 | 31.7°C | 26.1°C | 20.5°C | 36.6°C | 10.8°C | 92 mm | 70% | 2.2 m/s | 5.4 |
| 2015 | 34.7°C | 28.3°C | 21.8°C | 39.4°C | 17.1°C | 28 mm | 55% | 2.5 m/s | 5.6 |
| 2014 | 32.2°C | 26.3°C | 20.4°C | 39.6°C | 12.4°C | 29 mm | 63% | 2.3 m/s | 5 |
| 2013 | 34.3°C | 27.9°C | 21.6°C | 42.2°C | 12.6°C | 66 mm | 53% | 2.3 m/s | 5.2 |
| 2012 | 32.8°C | 26.0°C | 19.2°C | 41.4°C | 12.2°C | 74 mm | 57% | 2.6 m/s | 5.3 |
| 2011 | 34.1°C | 26.5°C | 18.9°C | 42.1°C | 11.9°C | 32 mm | 41% | 2.6 m/s | 6 |
| 2010 🌧️ | 30.3°C | 25.2°C | 20.1°C | 34.6°C | 9.3°C | 215 mm | 75% | 2.6 m/s | 5.3 |
| 2009 | 28.9°C | 23.7°C | 18.5°C | 38.7°C | 10.9°C | 168 mm | 73% | 2.5 m/s | 4.4 |
| 2008 | 30.5°C | 24.2°C | 17.8°C | 34.6°C | 10.9°C | 52 mm | 67% | 2.4 m/s | 5.3 |
| 2007 | 31.3°C | 25.7°C | 20.1°C | 34.6°C | 16.2°C | 107 mm | 72% | 2.3 m/s | 5.1 |
| 2006 | 31.3°C | 24.4°C | 17.4°C | 37.2°C | 11.3°C | 63 mm | 59% | 2.6 m/s | 5.3 |
| 2005 | 36.6°C | 29.2°C | 21.8°C | 41.5°C | 16.2°C | 20 mm | 48% | 2.8 m/s | 5.6 |
| 2004 | 32.3°C | 25.7°C | 19.1°C | 36.8°C | 12.9°C | 29 mm | 59% | 2.3 m/s | 5.5 |
| 2003 | 29.4°C | 23.4°C | 17.4°C | 34.2°C | 12.4°C | 94 mm | 69% | 2.4 m/s | 5 |
| 2002 | 33.6°C | 26.6°C | 19.6°C | 39.1°C | 11.8°C | 46 mm | 56% | 2.4 m/s | 5.4 |
| 2001 | 30.0°C | 24.0°C | 18.0°C | 34.4°C | 9.7°C | 61 mm | 70% | 2.5 m/s | 5.4 |
| 2000 | 35.2°C | 27.6°C | 20.0°C | 45.3°C | 8.1°C | 13 mm | 41% | 2.9 m/s | 5.8 |
| 1999 | 32.9°C | 25.8°C | 18.8°C | 38.2°C | 9.0°C | 43 mm | 50% | 3 m/s | 5.6 |
| 1998 | 35.6°C | 29.3°C | 23.0°C | 43.5°C | 18.3°C | 40 mm | 58% | 2.6 m/s | 5 |
| 1997 | 35.4°C | 28.4°C | 21.4°C | 40.3°C | 13.6°C | 22 mm | 48% | 2.9 m/s | 5.5 |
| 1996 | 28.4°C | 22.9°C | 17.3°C | 33.0°C | 7.7°C | 101 mm | 73% | 2.1 m/s | 4.9 |
| 1995 | 31.4°C | 25.2°C | 19.0°C | 42.4°C | 6.9°C | 96 mm | 63% | 2.6 m/s | 4.7 |
| 1994 | 29.9°C | 23.6°C | 17.3°C | 35.8°C | 7.7°C | 98 mm | 66% | 2.3 m/s | 5 |
| 1993 | 31.9°C | 24.9°C | 17.8°C | 36.1°C | 8.8°C | 113 mm | 60% | 2.7 m/s | 5.5 |
| 1992 | 32.2°C | 25.4°C | 18.5°C | 37.0°C | 9.3°C | 82 mm | 64% | 2.9 m/s | 5.4 |
| 1991 ❄️ | 28.1°C | 22.7°C | 17.4°C | 33.4°C | 7.6°C | 86 mm | 74% | 2.4 m/s | 4.6 |
| 1990 | 33.6°C | 27.6°C | 21.5°C | 41.2°C | 10.3°C | 58 mm | 59% | 2.3 m/s | 4.9 |
| 1989 | 29.9°C | 23.2°C | 16.4°C | 40.9°C | 4.9°C | 102 mm | 62% | 2.6 m/s | 5.3 |
| 1988 | 32.1°C | 25.3°C | 18.6°C | 37.5°C | 12.1°C | 136 mm | 62% | 2.5 m/s | 5.1 |
| 1987 | 31.8°C | 24.9°C | 18.0°C | 36.2°C | 12.1°C | 69 mm | 62% | 2.3 m/s | 5.4 |
| 1986 | 30.7°C | 25.7°C | 20.8°C | 34.5°C | 13.6°C | 128 mm | 76% | 3.3 m/s | 4.8 |
| 1985 | 32.2°C | 25.9°C | 19.5°C | 42.3°C | 4.8°C | 91 mm | 56% | 3.5 m/s | 5.2 |
| 1984 | 31.9°C | 24.9°C | 18.0°C | 39.0°C | 4.4°C | 34 mm | 52% | 3.4 m/s | 5 |
| 1983 | 33.8°C | 26.8°C | 19.8°C | 38.6°C | 8.2°C | 11 mm | 53% | 3.4 m/s | — |
| 1982 | 33.8°C | 26.6°C | 19.4°C | 39.4°C | 10.0°C | 24 mm | 48% | 3 m/s | — |
| 1981 | 31.5°C | 25.0°C | 18.6°C | 34.8°C | 8.3°C | 75 mm | 63% | 2.6 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 32.3°C with lows near 19.5°C (mean 25.9°C), based on 45 years of NASA POWER data.
September averages 72 mm of rainfall in Keller, about average for rainfall. The wettest on record was 215 mm in 2010.
The hottest September reached 45.3°C in 2000. The coldest dipped to 4.4°C in 1984.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.5°C. Daytime highs moved from 32.6°C to 34°C and overnight lows from 19.1°C to 20.6°C over the same span.
September is one of the warmer months of the year in Keller and about average for rainfall, so plan for around 32.3°C daytime highs and 19.5°C at night.
Not quite — September is the 9th coolest month in Keller, averaging 25.9°C.
For September in Keller, pack light, breathable clothing and sun protection, with typical highs of 32.3°C and lows of 19.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 61% — moderately humid.
Average wind speed in September is 2.6 m/s. The windiest September on record averaged 3.5 m/s (1985).
The wettest September on record was 2010 with 215 mm. On average, September sees 72 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 Keller 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.
