September is one of the cooler months of the year in Mount Barker, with average highs near 17.6°C and lows around 7.8°C (mean 12.7°C). It is a relatively wet time of year, averaging 48 mm of rainfall and 72% relative humidity across the period.
September is one of the cooler months of the year in Mount Barker. Across 45 years of records, the warmest September in Mount Barker was 2023 — when the month averaged 15.4°C — while the coldest was 1992 at 10.1°C. Typical September days reach 17.6°C with nights near 7.8°C. The long-term trend is warming, about 0.3°C per decade.
September is a relatively wet time of year in Mount Barker, averaging 48 mm of rainfall. The wettest September on record was 1992 with 113 mm, while the driest was 2018 at 11 mm.
Relative humidity in Mount Barker during September averages 72%. The most humid Septembers were 1992 and 2010 at 81%, and the least humid was 2023 at 61%.
September receives about 4.5 kWh/m²/day of solar energy in Mount Barker. The sunniest September was 2023 at 5.4 kWh/m²/day, and the cloudiest was 2010 at 3.7.
Average wind speed in Mount Barker during September is 2.6 m/s. The windiest September was 1996 at 3.4 m/s, while the calmest was 1997 at 2.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 12.1°C | 12.3°C | 12.9°C | 12.9°C | 13.5°C | +1.4°C |
| Avg High | 17.0°C | 17.1°C | 17.8°C | 17.9°C | 18.6°C | +1.6°C |
| Avg Low | 7.3°C | 7.5°C | 8.0°C | 7.9°C | 8.3°C | +1°C |
| Avg Rain | 43 mm | 63 mm | 51 mm | 43 mm | 35 mm | -8 mm |
September temperatures in Mount Barker have risen by about 1.5°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 1.8°C (1995) to a record high of 29.8°C (1987).
Rainfall in September is a relatively wet time of year, averaging 48 mm, with a wettest year of 113 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.4°C per decade while lows rose 0.2°C per decade, widening the gap between day and night.
A quieter season to visit Mount Barker
If your dates are flexible, the more temperate months of February and January tend to be the most comfortable for visiting Mount Barker. That said, September — with days averaging 17.6°C and nights around 7.8°C (mean 12.7°C) and moderate rainfall (48 mm) — can still be rewarding for travellers who don't mind the cooler conditions, and often means fewer crowds.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 18.1°C | 13.3°C | 8.6°C | 25.8°C | 5.0°C | 20 mm | 71% | 2.7 m/s | 4.5 |
| 2024 | 18.5°C | 13.3°C | 8.1°C | 27.4°C | 3.1°C | 25 mm | 69% | 2.8 m/s | 4.5 |
| 2023 🔥 | 21.7°C | 15.4°C | 9.1°C | 29.5°C | 5.9°C | 12 mm | 61% | 2.3 m/s | 5.4 |
| 2022 | 16.2°C | 12.0°C | 7.7°C | 21.9°C | 4.0°C | 69 mm | 80% | 2.5 m/s | 3.9 |
| 2021 | 18.3°C | 13.1°C | 8.0°C | 28.4°C | 3.6°C | 33 mm | 69% | 2.7 m/s | 4.6 |
| 2020 | 18.6°C | 13.6°C | 8.5°C | 27.0°C | 3.5°C | 52 mm | 71% | 2.8 m/s | 4.4 |
| 2019 | 18.8°C | 13.2°C | 7.5°C | 28.3°C | 2.9°C | 13 mm | 64% | 2.4 m/s | 4.6 |
| 2018 | 17.9°C | 12.2°C | 6.6°C | 24.8°C | 2.8°C | 11 mm | 64% | 2.5 m/s | 4.9 |
| 2017 | 18.1°C | 13.3°C | 8.5°C | 28.1°C | 3.7°C | 20 mm | 67% | 3.1 m/s | 4.6 |
| 2016 | 15.6°C | 11.6°C | 7.5°C | 22.6°C | 4.6°C | 107 mm | 77% | 2.7 m/s | 3.9 |
| 2015 | 18.2°C | 12.8°C | 7.4°C | 27.1°C | 4.1°C | 22 mm | 68% | 2.2 m/s | 4.6 |
| 2014 | 18.8°C | 13.5°C | 8.2°C | 27.0°C | 4.8°C | 27 mm | 70% | 2.4 m/s | 4.8 |
| 2013 | 19.3°C | 14.7°C | 10.1°C | 25.2°C | 6.4°C | 57 mm | 75% | 2.7 m/s | 4.1 |
| 2012 | 17.9°C | 12.8°C | 7.6°C | 25.3°C | 3.9°C | 32 mm | 71% | 2.7 m/s | 4.5 |
| 2011 | 18.9°C | 13.5°C | 8.2°C | 28.5°C | 4.3°C | 53 mm | 68% | 2.7 m/s | 4.6 |
| 2010 | 15.2°C | 11.4°C | 7.5°C | 18.6°C | 3.9°C | 92 mm | 81% | 2.3 m/s | 3.7 |
| 2009 | 17.7°C | 13.0°C | 8.2°C | 26.2°C | 4.7°C | 71 mm | 72% | 2.8 m/s | 4.2 |
| 2008 | 18.6°C | 12.9°C | 7.3°C | 29.5°C | 2.9°C | 29 mm | 68% | 2.6 m/s | 4.9 |
| 2007 | 18.9°C | 13.4°C | 7.9°C | 28.7°C | 2.4°C | 35 mm | 66% | 2.9 m/s | 4.7 |
| 2006 | 19.3°C | 13.7°C | 8.2°C | 28.1°C | 3.6°C | 27 mm | 64% | 2.7 m/s | 4.7 |
| 2005 | 17.3°C | 12.6°C | 8.0°C | 24.5°C | 4.6°C | 59 mm | 74% | 2.4 m/s | 4.5 |
| 2004 | 16.7°C | 12.2°C | 7.7°C | 27.0°C | 4.4°C | 50 mm | 77% | 2.2 m/s | 4.2 |
| 2003 | 16.0°C | 11.5°C | 7.1°C | 24.1°C | 2.3°C | 54 mm | 76% | 3.2 m/s | 4.6 |
| 2002 | 17.7°C | 12.8°C | 8.0°C | 28.2°C | 3.3°C | 39 mm | 67% | 3.2 m/s | 4.5 |
| 2001 | 18.1°C | 13.3°C | 8.4°C | 27.2°C | 3.6°C | 92 mm | 76% | 2.5 m/s | 4.1 |
| 2000 | 17.6°C | 13.2°C | 8.7°C | 26.1°C | 5.3°C | 58 mm | 77% | 2.9 m/s | 4.2 |
| 1999 | 19.8°C | 14.3°C | 8.7°C | 29.8°C | 4.3°C | 57 mm | 69% | 2.5 m/s | 4.5 |
| 1998 | 18.6°C | 13.2°C | 7.9°C | 27.0°C | 4.0°C | 47 mm | 73% | 2.5 m/s | 4.5 |
| 1997 | 17.0°C | 12.4°C | 7.8°C | 22.5°C | 4.1°C | 83 mm | 77% | 2.1 m/s | 4.3 |
| 1996 | 15.5°C | 11.4°C | 7.3°C | 24.8°C | 2.7°C | 89 mm | 75% | 3.4 m/s | 4.4 |
| 1995 | 17.2°C | 12.2°C | 7.2°C | 23.9°C | 1.8°C | 35 mm | 74% | 2.3 m/s | 4.2 |
| 1994 | 16.0°C | 11.5°C | 7.0°C | 23.0°C | 3.0°C | 23 mm | 71% | 2.4 m/s | 4.5 |
| 1993 | 17.5°C | 12.6°C | 7.6°C | 25.0°C | 2.4°C | 65 mm | 72% | 2.3 m/s | 4.5 |
| 1992 ❄️ 🌧️ | 13.8°C | 10.1°C | 6.5°C | 18.1°C | 4.3°C | 113 mm | 81% | 2.4 m/s | 4.1 |
| 1991 | 17.4°C | 12.4°C | 7.5°C | 24.5°C | 4.9°C | 72 mm | 75% | 2.8 m/s | 4.3 |
| 1990 | 18.1°C | 12.9°C | 7.7°C | 27.2°C | 4.2°C | 43 mm | 73% | 2.5 m/s | 4.6 |
| 1989 | 16.6°C | 11.9°C | 7.2°C | 24.7°C | 4.7°C | 44 mm | 77% | 2.6 m/s | 4.7 |
| 1988 | 18.5°C | 13.3°C | 8.2°C | 26.6°C | 3.4°C | 51 mm | 67% | 2.8 m/s | 4.7 |
| 1987 | 18.0°C | 12.8°C | 7.7°C | 29.8°C | 3.0°C | 17 mm | 72% | 2.2 m/s | 4.5 |
| 1986 | 16.1°C | 11.8°C | 7.5°C | 22.8°C | 4.3°C | 59 mm | 78% | 2.7 m/s | 4.6 |
| 1985 | 16.1°C | 11.3°C | 6.5°C | 22.9°C | 4.0°C | 51 mm | 73% | 2.5 m/s | 4.7 |
| 1984 | 14.5°C | 10.4°C | 6.3°C | 22.6°C | 2.2°C | 53 mm | 75% | 2.7 m/s | 4.3 |
| 1983 | 16.8°C | 11.9°C | 7.1°C | 25.4°C | 2.6°C | 58 mm | 77% | 2.8 m/s | — |
| 1982 | 17.5°C | 12.2°C | 7.0°C | 25.0°C | 4.6°C | 27 mm | 66% | 2.5 m/s | — |
| 1981 | 18.6°C | 13.5°C | 8.4°C | 27.6°C | 4.5°C | 27 mm | 72% | 2.5 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 17.6°C with lows near 7.8°C (mean 12.7°C), based on 45 years of NASA POWER data.
September averages 48 mm of rainfall in Mount Barker, a relatively wet time of year. The wettest on record was 113 mm in 1992.
The hottest September reached 29.8°C in 1987. The coldest dipped to 1.8°C in 1995.
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 16.7°C to 18.6°C and overnight lows from 7.1°C to 8.3°C over the same span.
September is one of the cooler months of the year in Mount Barker and a relatively wet time of year, so plan for around 17.6°C daytime highs and 7.8°C at night.
Not quite — September is the 4th coolest month in Mount Barker, averaging 12.7°C.
For September in Mount Barker, pack warm layers and a jacket for chilly mornings, with typical highs of 17.6°C and lows of 7.8°C.
Relative humidity in September averages 72% — moderately humid.
Average wind speed in September is 2.6 m/s. The windiest September on record averaged 3.4 m/s (1996).
The wettest September on record was 1992 with 113 mm. On average, September sees 48 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 Mount Barker 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.
