September is one of the cooler months of the year in Kwinana, with average highs near 18.3°C and lows around 13.6°C (mean 16°C). It is a relatively wet time of year, averaging 72 mm of rainfall and 74% relative humidity across the period.
September is one of the cooler months of the year in Kwinana. Across 45 years of records, the warmest September in Kwinana was 2023 — when the month averaged 17.4°C — while the coldest was 2016 at 14.3°C. Typical September days reach 18.3°C with nights near 13.6°C. The long-term September temperature trend is broadly flat.
September is a relatively wet time of year in Kwinana, averaging 72 mm of rainfall. The wettest Septembers on record were 1982 and 2013 with 147 mm, while the driest was 2019 at 14 mm.
Relative humidity in Kwinana during September averages 74%. The most humid September was 1997 at 77%, and the least humid was 2010 at 68%.
September receives about 4.8 kWh/m²/day of solar energy in Kwinana. The sunniest Septembers were 2010 and 2024 at 5.4 kWh/m²/day, and the cloudiest was 2001 at 4.1.
Average wind speed in Kwinana during September is 5.1 m/s. The windiest September was 2013 at 6 m/s, while the calmest were 1986 and 2019 at 4.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.2°C | 15.8°C | 15.6°C | 16.0°C | 16.5°C | +0.3°C |
| Avg High | 18.6°C | 18.0°C | 17.7°C | 18.5°C | 19.1°C | +0.5°C |
| Avg Low | 13.8°C | 13.6°C | 13.5°C | 13.5°C | 14.0°C | +0.2°C |
| Avg Rain | 75 mm | 92 mm | 79 mm | 60 mm | 44 mm | -31 mm |
September temperatures in Kwinana have risen by about 0.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 8.4°C (2005) to a record high of 30.2°C (2023).
Rainfall in September is a relatively wet time of year, averaging 72 mm, with a wettest year of 147 mm.
A quieter season to visit Kwinana
If your dates are flexible, the more temperate months of December and March tend to be the most comfortable for visiting Kwinana. That said, September — with days averaging 18.3°C and nights around 13.6°C (mean 16°C) and moderate rainfall (72 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 | 18.8°C | 16.3°C | 13.8°C | 24.6°C | 10.1°C | 63 mm | 73% | 4.8 m/s | 5.2 |
| 2024 | 19.8°C | 16.9°C | 14.0°C | 25.2°C | 11.7°C | 20 mm | 71% | 5.1 m/s | 5.4 |
| 2023 🔥 | 19.7°C | 17.4°C | 15.1°C | 30.2°C | 9.9°C | 45 mm | 75% | 5 m/s | 4.8 |
| 2022 | 18.4°C | 16.0°C | 13.6°C | 23.4°C | 11.3°C | 47 mm | 74% | 4.9 m/s | 4.8 |
| 2021 | 18.8°C | 16.0°C | 13.2°C | 24.6°C | 10.1°C | 40 mm | 73% | 4.9 m/s | 5.2 |
| 2020 | 19.0°C | 16.6°C | 14.2°C | 24.2°C | 11.5°C | 50 mm | 72% | 5.5 m/s | 4.7 |
| 2019 | 19.7°C | 16.8°C | 13.9°C | 25.3°C | 9.5°C | 14 mm | 74% | 4.4 m/s | 5.2 |
| 2018 | 17.8°C | 15.5°C | 13.2°C | 22.6°C | 9.0°C | 26 mm | 74% | 4.6 m/s | 4.9 |
| 2017 | 18.3°C | 15.9°C | 13.6°C | 24.3°C | 10.2°C | 60 mm | 75% | 4.6 m/s | 4.8 |
| 2016 ❄️ | 16.4°C | 14.3°C | 12.1°C | 18.7°C | 9.3°C | 48 mm | 72% | 5 m/s | 4.7 |
| 2015 | 19.5°C | 16.1°C | 12.7°C | 25.5°C | 9.8°C | 22 mm | 71% | 4.8 m/s | 5.3 |
| 2014 | 19.5°C | 17.1°C | 14.8°C | 25.6°C | 12.3°C | 75 mm | 76% | 5 m/s | 4.5 |
| 2013 | 17.9°C | 16.4°C | 14.9°C | 20.2°C | 12.8°C | 147 mm | 75% | 6 m/s | 4.2 |
| 2012 | 18.5°C | 15.8°C | 13.0°C | 25.3°C | 9.9°C | 90 mm | 72% | 5.4 m/s | 4.9 |
| 2011 | 18.5°C | 16.1°C | 13.6°C | 21.0°C | 10.6°C | 94 mm | 73% | 5 m/s | 4.8 |
| 2010 | 19.3°C | 16.1°C | 12.8°C | 25.2°C | 10.1°C | 21 mm | 68% | 4.7 m/s | 5.4 |
| 2009 | 16.8°C | 15.0°C | 13.2°C | 20.4°C | 10.1°C | 105 mm | 73% | 5.9 m/s | 4.4 |
| 2008 | 18.1°C | 15.8°C | 13.6°C | 21.2°C | 9.3°C | 68 mm | 74% | 5.3 m/s | 4.7 |
| 2007 | 17.9°C | 16.0°C | 14.1°C | 21.9°C | 11.4°C | 93 mm | 75% | 5.1 m/s | 4.4 |
| 2006 | 18.4°C | 16.0°C | 13.7°C | 23.7°C | 9.8°C | 49 mm | 75% | 5.2 m/s | 4.7 |
| 2005 | 17.1°C | 15.1°C | 13.2°C | 20.7°C | 8.4°C | 104 mm | 73% | 5.6 m/s | 4.7 |
| 2004 | 17.4°C | 14.8°C | 12.2°C | 21.2°C | 8.9°C | 43 mm | 74% | 4.7 m/s | 5 |
| 2003 | 17.3°C | 15.2°C | 13.1°C | 22.2°C | 11.0°C | 103 mm | 75% | 5.5 m/s | 4.7 |
| 2002 | 17.4°C | 15.4°C | 13.3°C | 23.4°C | 9.9°C | 72 mm | 74% | 5.3 m/s | 4.8 |
| 2001 | 17.7°C | 15.8°C | 13.9°C | 21.5°C | 11.2°C | 112 mm | 75% | 5 m/s | 4.1 |
| 2000 | 18.6°C | 16.6°C | 14.6°C | 23.0°C | 11.9°C | 47 mm | 76% | 4.7 m/s | 4.5 |
| 1999 | 17.9°C | 15.6°C | 13.3°C | 22.4°C | 9.5°C | 131 mm | 75% | 5.2 m/s | 4.5 |
| 1998 | 17.9°C | 15.6°C | 13.4°C | 21.7°C | 9.8°C | 130 mm | 71% | 5.6 m/s | 4.7 |
| 1997 | 18.0°C | 16.0°C | 14.0°C | 22.2°C | 11.3°C | 110 mm | 77% | 4.6 m/s | 4.8 |
| 1996 | 18.2°C | 16.5°C | 14.7°C | 20.2°C | 11.2°C | 128 mm | 73% | 5.9 m/s | 4.5 |
| 1995 | 18.3°C | 16.4°C | 14.5°C | 21.3°C | 11.3°C | 75 mm | 74% | 4.5 m/s | 4.6 |
| 1994 | 19.2°C | 16.2°C | 13.3°C | 24.5°C | 10.5°C | 60 mm | 74% | 5.1 m/s | 5.1 |
| 1993 | 17.7°C | 15.5°C | 13.2°C | 21.7°C | 10.9°C | 97 mm | 74% | 4.9 m/s | 4.9 |
| 1992 | 16.3°C | 14.4°C | 12.5°C | 20.9°C | 9.9°C | 61 mm | 77% | 5.5 m/s | 4.7 |
| 1991 | 17.8°C | 16.0°C | 14.2°C | 21.1°C | 10.9°C | 69 mm | 75% | 4.9 m/s | 4.5 |
| 1990 | 18.7°C | 15.9°C | 13.1°C | 26.2°C | 9.4°C | 58 mm | 73% | 4.6 m/s | 4.6 |
| 1989 | 18.5°C | 16.5°C | 14.5°C | 21.9°C | 10.6°C | 71 mm | 72% | 5.1 m/s | 4.5 |
| 1988 | 18.8°C | 16.8°C | 14.9°C | 24.0°C | 11.8°C | 73 mm | 73% | 5.4 m/s | 4.6 |
| 1987 | 19.4°C | 16.4°C | 13.4°C | 24.2°C | 10.2°C | 33 mm | 73% | 4.7 m/s | 5.2 |
| 1986 | 18.0°C | 15.8°C | 13.7°C | 23.0°C | 11.3°C | 58 mm | 75% | 4.4 m/s | 4.4 |
| 1985 | 19.0°C | 15.9°C | 12.9°C | 24.5°C | 9.7°C | 55 mm | 74% | 5 m/s | 5.2 |
| 1984 | 18.4°C | 15.8°C | 13.1°C | 20.6°C | 9.7°C | 97 mm | 71% | 5.2 m/s | 5.2 |
| 1983 | 18.8°C | 16.9°C | 15.1°C | 22.9°C | 12.0°C | 85 mm | 74% | 5.2 m/s | — |
| 1982 🌧️ | 18.5°C | 15.8°C | 13.2°C | 25.9°C | 9.5°C | 147 mm | 73% | 4.8 m/s | — |
| 1981 | 18.2°C | 15.9°C | 13.7°C | 22.6°C | 8.5°C | 55 mm | 76% | 4.8 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 18.3°C with lows near 13.6°C (mean 16°C), based on 45 years of NASA POWER data.
September averages 72 mm of rainfall in Kwinana, a relatively wet time of year. The wettest on record was 147 mm in 1982.
The hottest September reached 30.2°C in 2023. The coldest dipped to 8.4°C in 2005.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 0.4°C. Daytime highs moved from 18.6°C to 19.1°C and overnight lows from 13.6°C to 13.9°C over the same span.
September is one of the cooler months of the year in Kwinana and a relatively wet time of year, so plan for around 18.3°C daytime highs and 13.6°C at night.
Not quite — September is the 3rd coolest month in Kwinana, averaging 16°C.
For September in Kwinana, pack light layers you can adjust through the day, with typical highs of 18.3°C and lows of 13.6°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 74% — moderately humid.
Average wind speed in September is 5.1 m/s. The windiest September on record averaged 6 m/s (2013).
The wettest September on record was 1982 with 147 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 Kwinana 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.
