September is one of the cooler months of the year in Onslow, with average highs near 26.2°C and lows around 19°C (mean 22.6°C). It is one of the drier months, averaging 2 mm of rainfall and 62% relative humidity across the period.
September is one of the cooler months of the year in Onslow. Across 45 years of records, the warmest September in Onslow was 2024 — when the month averaged 24.7°C — while the coldest were 1992 and 2005 at 21.2°C. Typical September days reach 26.2°C with nights near 19°C. The long-term trend is warming, about 0.2°C per decade.
September is one of the drier months in Onslow, averaging 2 mm of rainfall. The wettest September on record was 2022 with 10 mm, while the driest were 2020, 2021 and 2023, among others at 0 mm.
Relative humidity in Onslow during September averages 62%. The most humid September was 1995 at 66%, and the least humid were 2010 and 2011 at 57%.
September receives about 6.4 kWh/m²/day of solar energy in Onslow. The sunniest September was 2002 at 6.9 kWh/m²/day, and the cloudiest were 2001 and 2024 at 5.9.
Average wind speed in Onslow during September is 4.8 m/s. The windiest September was 1991 at 5.4 m/s, while the calmest was 2015 at 3.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 22.8°C | 22.1°C | 22.3°C | 22.7°C | 23.4°C | +0.6°C |
| Avg High | 26.4°C | 25.5°C | 25.9°C | 26.2°C | 27.0°C | +0.6°C |
| Avg Low | 19.1°C | 18.6°C | 18.7°C | 19.2°C | 19.9°C | +0.8°C |
| Avg Rain | 2 mm | 1 mm | 1 mm | 2 mm | 3 mm | +2 mm |
September temperatures in Onslow have risen by about 0.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 14.7°C (1991) to a record high of 32.4°C (2015).
Rainfall in September is one of the drier months, averaging 2 mm, with a wettest year of 10 mm.
One of the best times to visit Onslow
September is one of the best times to visit Onslow. Expect days averaging 26.2°C and nights around 19°C (mean 22.6°C) — cooler than Onslow's yearly average — with low rainfall (2 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 | 23.1°C | 19.5°C | 31.3°C | 16.4°C | 1 mm | 58% | 4.4 m/s | 6.6 |
| 2024 🔥 | 27.8°C | 24.7°C | 21.7°C | 30.4°C | 17.5°C | 9 mm | 60% | 4 m/s | 5.9 |
| 2023 | 27.6°C | 24.0°C | 20.4°C | 31.6°C | 17.7°C | 0 mm | 63% | 4.6 m/s | 6.5 |
| 2022 🌧️ | 25.2°C | 22.0°C | 18.8°C | 28.4°C | 16.4°C | 10 mm | 64% | 4.8 m/s | 6.5 |
| 2021 | 26.6°C | 22.8°C | 19.1°C | 31.2°C | 16.2°C | 0 mm | 57% | 4.9 m/s | 6.6 |
| 2020 | 27.8°C | 23.9°C | 20.0°C | 31.4°C | 17.5°C | 0 mm | 58% | 5.1 m/s | 6.6 |
| 2019 | 26.7°C | 23.1°C | 19.5°C | 29.3°C | 17.5°C | 1 mm | 62% | 4.4 m/s | 6.7 |
| 2018 | 26.4°C | 22.5°C | 18.6°C | 32.0°C | 15.5°C | 0 mm | 58% | 4.7 m/s | 6.8 |
| 2017 | 26.6°C | 23.2°C | 19.8°C | 31.4°C | 17.0°C | 6 mm | 62% | 4.9 m/s | 6.5 |
| 2016 | 25.3°C | 21.6°C | 17.9°C | 26.7°C | 16.3°C | 0 mm | 61% | 4.9 m/s | 6.7 |
| 2015 | 27.5°C | 23.7°C | 20.0°C | 32.4°C | 16.4°C | 0 mm | 59% | 3.9 m/s | 6.6 |
| 2014 | 26.2°C | 23.1°C | 19.9°C | 28.0°C | 18.0°C | 1 mm | 66% | 4.5 m/s | 6.4 |
| 2013 | 25.8°C | 22.3°C | 18.8°C | 29.4°C | 16.3°C | 0 mm | 64% | 5.3 m/s | 6.5 |
| 2012 | 25.9°C | 22.7°C | 19.4°C | 29.4°C | 16.2°C | 0 mm | 66% | 4.8 m/s | 6.5 |
| 2011 | 25.9°C | 22.3°C | 18.6°C | 27.8°C | 16.5°C | 0 mm | 57% | 4.8 m/s | 6.6 |
| 2010 | 26.1°C | 22.7°C | 19.3°C | 31.2°C | 16.1°C | 6 mm | 57% | 4.3 m/s | 6 |
| 2009 | 25.6°C | 21.7°C | 17.8°C | 31.6°C | 16.1°C | 0 mm | 59% | 5.3 m/s | 6.6 |
| 2008 | 26.4°C | 22.8°C | 19.2°C | 28.8°C | 17.7°C | 1 mm | 62% | 4.8 m/s | 6.3 |
| 2007 | 26.8°C | 22.7°C | 18.7°C | 31.8°C | 16.8°C | 0 mm | 60% | 5 m/s | 6.6 |
| 2006 | 26.8°C | 23.4°C | 20.1°C | 30.3°C | 18.5°C | 4 mm | 65% | 4.2 m/s | 6.4 |
| 2005 | 24.8°C | 21.2°C | 17.7°C | 28.8°C | 15.3°C | 1 mm | 66% | 5.3 m/s | 6.5 |
| 2004 | 25.3°C | 21.7°C | 18.1°C | 27.8°C | 15.3°C | 0 mm | 61% | 5 m/s | 6.5 |
| 2003 | 25.3°C | 21.8°C | 18.3°C | 27.2°C | 15.5°C | 0 mm | 64% | 5.3 m/s | 6.6 |
| 2002 | 25.6°C | 22.0°C | 18.4°C | 28.6°C | 16.3°C | 2 mm | 62% | 5 m/s | 6.9 |
| 2001 | 25.7°C | 22.5°C | 19.3°C | 29.1°C | 16.2°C | 0 mm | 61% | 4.7 m/s | 5.9 |
| 2000 | 27.1°C | 23.3°C | 19.5°C | 31.6°C | 16.0°C | 1 mm | 59% | 4.3 m/s | 6.3 |
| 1999 | 25.7°C | 22.4°C | 19.0°C | 29.0°C | 15.7°C | 1 mm | 65% | 5 m/s | 6.4 |
| 1998 | 25.7°C | 22.1°C | 18.5°C | 29.3°C | 16.2°C | 0 mm | 64% | 5.2 m/s | 6.2 |
| 1997 | 25.0°C | 21.5°C | 18.1°C | 27.4°C | 16.1°C | 6 mm | 66% | 5.1 m/s | 6.4 |
| 1996 | 25.6°C | 22.1°C | 18.6°C | 28.7°C | 17.5°C | 1 mm | 66% | 5.1 m/s | 6.5 |
| 1995 | 25.0°C | 22.1°C | 19.2°C | 27.3°C | 16.3°C | 2 mm | 66% | 5 m/s | 6.2 |
| 1994 | 26.9°C | 22.9°C | 19.0°C | 28.4°C | 16.7°C | 0 mm | 63% | 5.1 m/s | 6.5 |
| 1993 | 25.5°C | 22.0°C | 18.5°C | 29.3°C | 15.0°C | 0 mm | 58% | 4.8 m/s | 6.6 |
| 1992 ❄️ | 24.5°C | 21.2°C | 17.9°C | 27.5°C | 15.0°C | 1 mm | 62% | 5.2 m/s | 6 |
| 1991 | 25.4°C | 21.7°C | 18.0°C | 29.1°C | 14.7°C | 0 mm | 61% | 5.4 m/s | 6.5 |
| 1990 | 26.2°C | 22.6°C | 19.0°C | 30.5°C | 17.0°C | 0 mm | 60% | 4.3 m/s | 6.6 |
| 1989 | 27.3°C | 23.2°C | 19.1°C | 29.4°C | 17.1°C | 0 mm | 60% | 4.9 m/s | 6.5 |
| 1988 | 26.7°C | 22.7°C | 18.8°C | 29.9°C | 17.2°C | 0 mm | 61% | 4.9 m/s | 6.6 |
| 1987 | 27.0°C | 23.3°C | 19.6°C | 30.3°C | 17.6°C | 0 mm | 60% | 4.3 m/s | 6.2 |
| 1986 | 25.0°C | 21.4°C | 17.9°C | 27.7°C | 15.8°C | 6 mm | 63% | 4.9 m/s | 6.2 |
| 1985 | 26.4°C | 22.7°C | 19.0°C | 30.1°C | 16.4°C | 0 mm | 61% | 4.9 m/s | 6.4 |
| 1984 | 25.2°C | 22.0°C | 18.8°C | 27.3°C | 16.1°C | 2 mm | 63% | 4.8 m/s | 6.3 |
| 1983 | 27.3°C | 23.5°C | 19.8°C | 31.1°C | 17.0°C | 5 mm | 63% | 4.8 m/s | — |
| 1982 | 25.4°C | 22.4°C | 19.3°C | 29.2°C | 17.1°C | 2 mm | 63% | 4.8 m/s | — |
| 1981 | 27.6°C | 23.8°C | 20.0°C | 30.2°C | 17.3°C | 2 mm | 60% | 5 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 26.2°C with lows near 19°C (mean 22.6°C), based on 45 years of NASA POWER data.
September averages 2 mm of rainfall in Onslow, one of the drier months. The wettest on record was 10 mm in 2022.
The hottest September reached 32.4°C in 2015. The coldest dipped to 14.7°C in 1991.
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 26.4°C to 26.8°C and overnight lows from 19.4°C to 19.9°C over the same span.
September is one of the cooler months of the year in Onslow and one of the drier months, so plan for around 26.2°C daytime highs and 19°C at night.
Not quite — September is the 4th coolest month in Onslow, averaging 22.6°C.
For September in Onslow, pack light layers you can adjust through the day, with typical highs of 26.2°C and lows of 19°C.
Relative humidity in September averages 62% — moderately humid.
Average wind speed in September is 4.8 m/s. The windiest September on record averaged 5.4 m/s (1991).
The wettest September on record was 2022 with 10 mm. On average, September sees 2 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 Onslow 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.
