September is one of the cooler months of the year in Sunbury, with average highs near 15.3°C and lows around 5.1°C (mean 10.2°C). It is about average for rainfall, averaging 65 mm of rainfall and 80% relative humidity across the period.
September is one of the cooler months of the year in Sunbury. Across 45 years of records, the warmest September in Sunbury was 2023 — when the month averaged 13°C — while the coldest was 1992 at 8°C. Typical September days reach 15.3°C with nights near 5.1°C. The long-term trend is warming, about 0.4°C per decade.
September is about average for rainfall in Sunbury, averaging 65 mm of rainfall. The wettest September on record was 1993 with 153 mm, while the driest was 2018 at 17 mm.
Relative humidity in Sunbury during September averages 80%. The most humid September was 1992 at 88%, and the least humid was 2023 at 69%.
September receives about 4.1 kWh/m²/day of solar energy in Sunbury. The sunniest September was 2023 at 4.7 kWh/m²/day, and the cloudiest was 2022 at 3.4.
Average wind speed in Sunbury during September is 2.3 m/s. The windiest September was 1996 at 3 m/s, while the calmest was 1997 at 1.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 9.7°C | 9.6°C | 10.5°C | 10.4°C | 11.1°C | +1.4°C |
| Avg High | 14.7°C | 14.3°C | 15.8°C | 15.6°C | 16.5°C | +1.8°C |
| Avg Low | 4.7°C | 4.8°C | 5.2°C | 5.2°C | 5.8°C | +1.1°C |
| Avg Rain | 68 mm | 85 mm | 61 mm | 56 mm | 46 mm | -22 mm |
September temperatures in Sunbury have risen by about 1.7°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -1.1°C (2013) to a record high of 28.6°C (2017).
Rainfall in September is about average for rainfall, averaging 65 mm, with a wettest year of 153 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.5°C per decade while lows rose 0.3°C per decade, widening the gap between day and night.
A quieter season to visit Sunbury
If your dates are flexible, the more temperate months of February and January tend to be the most comfortable for visiting Sunbury. That said, September — with days averaging 15.3°C and nights around 5.1°C (mean 10.2°C) and moderate rainfall (65 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 | 16.6°C | 11.2°C | 5.7°C | 21.7°C | 1.2°C | 24 mm | 74% | 2.6 m/s | 4 |
| 2024 | 16.7°C | 11.3°C | 5.9°C | 24.6°C | 2.2°C | 45 mm | 73% | 2.8 m/s | 4 |
| 2023 🔥 | 19.6°C | 13.0°C | 6.5°C | 27.4°C | 2.2°C | 20 mm | 69% | 2.2 m/s | 4.7 |
| 2022 | 14.5°C | 10.1°C | 5.7°C | 19.2°C | 0.2°C | 56 mm | 85% | 2.2 m/s | 3.4 |
| 2021 | 15.8°C | 10.6°C | 5.4°C | 21.4°C | 1.9°C | 86 mm | 79% | 2.5 m/s | 4.3 |
| 2020 | 15.6°C | 10.5°C | 5.4°C | 21.4°C | 1.2°C | 42 mm | 80% | 2.5 m/s | 4.2 |
| 2019 | 16.3°C | 10.8°C | 5.2°C | 23.0°C | 1.3°C | 40 mm | 76% | 2.2 m/s | 4.2 |
| 2018 | 16.4°C | 10.1°C | 3.9°C | 22.9°C | 0.9°C | 17 mm | 72% | 2.2 m/s | 4.5 |
| 2017 | 16.0°C | 10.5°C | 4.9°C | 28.6°C | 0.0°C | 38 mm | 73% | 2.9 m/s | 4.1 |
| 2016 | 14.3°C | 10.1°C | 5.9°C | 19.3°C | 3.2°C | 89 mm | 85% | 2.2 m/s | 3.5 |
| 2015 | 15.9°C | 10.4°C | 4.9°C | 22.6°C | 2.3°C | 24 mm | 78% | 2.1 m/s | 4.2 |
| 2014 | 15.9°C | 10.8°C | 5.6°C | 23.2°C | 2.2°C | 58 mm | 80% | 2.2 m/s | 4.3 |
| 2013 | 16.4°C | 11.6°C | 6.8°C | 22.4°C | -1.1°C | 83 mm | 81% | 2.3 m/s | 3.9 |
| 2012 | 15.2°C | 10.3°C | 5.3°C | 21.2°C | 1.0°C | 48 mm | 80% | 2.3 m/s | 4.2 |
| 2011 | 16.0°C | 10.7°C | 5.4°C | 23.3°C | 2.4°C | 81 mm | 78% | 2.5 m/s | 4.2 |
| 2010 | 13.5°C | 9.0°C | 4.5°C | 17.9°C | 1.1°C | 84 mm | 86% | 2.2 m/s | 3.6 |
| 2009 | 15.5°C | 10.3°C | 5.2°C | 23.5°C | 2.1°C | 100 mm | 78% | 2.6 m/s | 3.9 |
| 2008 | 16.3°C | 10.6°C | 4.9°C | 25.3°C | 1.6°C | 25 mm | 73% | 2.4 m/s | 4.5 |
| 2007 | 15.6°C | 10.2°C | 4.8°C | 18.7°C | 0.9°C | 39 mm | 76% | 2.5 m/s | 4.4 |
| 2006 | 17.6°C | 11.6°C | 5.6°C | 25.6°C | 0.9°C | 43 mm | 70% | 2.4 m/s | 4.4 |
| 2005 | 15.2°C | 10.4°C | 5.5°C | 20.0°C | 0.6°C | 64 mm | 81% | 2.2 m/s | 3.9 |
| 2004 | 14.9°C | 10.2°C | 5.5°C | 20.8°C | 0.9°C | 84 mm | 85% | 1.9 m/s | 3.7 |
| 2003 | 14.2°C | 9.1°C | 4.1°C | 20.9°C | -0.6°C | 50 mm | 81% | 2.7 m/s | 4.3 |
| 2002 | 16.4°C | 10.7°C | 4.9°C | 24.1°C | 1.6°C | 52 mm | 71% | 2.8 m/s | 4.1 |
| 2001 | 16.8°C | 11.5°C | 6.2°C | 24.5°C | 1.3°C | 50 mm | 80% | 2.2 m/s | 3.9 |
| 2000 | 15.3°C | 10.4°C | 5.5°C | 19.9°C | 1.0°C | 105 mm | 83% | 2.4 m/s | 3.9 |
| 1999 | 16.6°C | 11.5°C | 6.4°C | 22.1°C | 1.7°C | 49 mm | 80% | 2.3 m/s | 4.2 |
| 1998 | 16.1°C | 10.9°C | 5.8°C | 23.3°C | 1.2°C | 66 mm | 81% | 2.4 m/s | 4 |
| 1997 | 15.1°C | 10.2°C | 5.3°C | 18.0°C | 1.3°C | 76 mm | 82% | 1.8 m/s | 4.2 |
| 1996 | 13.5°C | 9.0°C | 4.4°C | 20.1°C | -0.9°C | 116 mm | 84% | 3 m/s | 3.8 |
| 1995 | 13.9°C | 8.9°C | 3.8°C | 18.9°C | 0.6°C | 44 mm | 85% | 2 m/s | 3.9 |
| 1994 | 13.5°C | 8.5°C | 3.4°C | 19.4°C | 0.9°C | 54 mm | 78% | 2.3 m/s | 4 |
| 1993 🌧️ | 14.2°C | 9.8°C | 5.4°C | 21.6°C | 0.9°C | 153 mm | 87% | 2.3 m/s | 3.9 |
| 1992 ❄️ | 11.8°C | 8.0°C | 4.2°C | 15.1°C | 0.8°C | 136 mm | 88% | 2.2 m/s | 3.6 |
| 1991 | 13.8°C | 9.0°C | 4.3°C | 18.6°C | 0.4°C | 98 mm | 85% | 2.3 m/s | 4.1 |
| 1990 | 14.7°C | 9.8°C | 4.9°C | 20.1°C | 1.6°C | 56 mm | 83% | 2.3 m/s | 4.3 |
| 1989 | 14.2°C | 9.4°C | 4.7°C | 20.6°C | 1.0°C | 59 mm | 85% | 2.4 m/s | 4.3 |
| 1988 | 15.4°C | 10.4°C | 5.3°C | 20.5°C | 2.3°C | 79 mm | 82% | 2.5 m/s | 4.1 |
| 1987 | 15.8°C | 10.6°C | 5.4°C | 24.4°C | 1.0°C | 43 mm | 82% | 2.2 m/s | 4.2 |
| 1986 | 14.0°C | 9.5°C | 5.0°C | 19.3°C | 2.4°C | 68 mm | 86% | 2.2 m/s | 3.8 |
| 1985 | 14.1°C | 9.4°C | 4.7°C | 19.1°C | 1.9°C | 54 mm | 84% | 2.1 m/s | 4.3 |
| 1984 | 13.0°C | 8.7°C | 4.4°C | 18.1°C | 1.4°C | 112 mm | 84% | 2.3 m/s | 3.9 |
| 1983 | 13.9°C | 9.3°C | 4.6°C | 19.2°C | 1.5°C | 108 mm | 86% | 2.5 m/s | — |
| 1982 | 15.7°C | 9.5°C | 3.4°C | 22.9°C | -0.4°C | 53 mm | 73% | 2.2 m/s | — |
| 1981 | 15.9°C | 10.5°C | 5.2°C | 22.9°C | 2.0°C | 35 mm | 85% | 2.2 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 15.3°C with lows near 5.1°C (mean 10.2°C), based on 45 years of NASA POWER data.
September averages 65 mm of rainfall in Sunbury, about average for rainfall. The wettest on record was 153 mm in 1993.
The hottest September reached 28.6°C in 2017. The coldest dipped to -1.1°C in 2013.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.7°C. Daytime highs moved from 14.5°C to 16.6°C and overnight lows from 4.5°C to 5.8°C over the same span.
September is one of the cooler months of the year in Sunbury and about average for rainfall, so plan for around 15.3°C daytime highs and 5.1°C at night.
Not quite — September is the 4th coolest month in Sunbury, averaging 10.2°C.
For September in Sunbury, pack warm layers and a jacket for chilly mornings, with typical highs of 15.3°C and lows of 5.1°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 80% — quite humid.
Average wind speed in September is 2.3 m/s. The windiest September on record averaged 3 m/s (1996).
The wettest September on record was 1993 with 153 mm. On average, September sees 65 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 Sunbury 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.
