September is one of the cooler months of the year in Merredin, with average highs near 20.8°C and lows around 6.8°C (mean 13.8°C). It is about average for rainfall, averaging 27 mm of rainfall and 69% relative humidity across the period.
September is one of the cooler months of the year in Merredin. Across 45 years of records, the warmest September in Merredin was 2023 — when the month averaged 16.5°C — while the coldest was 1992 at 11.1°C. Typical September days reach 20.8°C with nights near 6.8°C. The long-term September temperature trend is broadly flat.
September is about average for rainfall in Merredin, averaging 27 mm of rainfall. The wettest September on record was 2013 with 59 mm, while the driest was 2010 at 5 mm.
Relative humidity in Merredin during September averages 69%. The most humid September was 1992 at 80%, and the least humid was 2010 at 59%.
September receives about 5.3 kWh/m²/day of solar energy in Merredin. The sunniest September was 2019 at 5.9 kWh/m²/day, and the cloudiest was 1992 at 4.6.
Average wind speed in Merredin during September is 2.9 m/s. The windiest September was 1996 at 3.5 m/s, while the calmest were 1995 and 1997 at 2.5 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.0°C | 13.4°C | 13.6°C | 14.1°C | 13.9°C | -0.1°C |
| Avg High | 21.2°C | 20.2°C | 20.6°C | 21.3°C | 20.8°C | -0.4°C |
| Avg Low | 6.9°C | 6.6°C | 6.6°C | 6.9°C | 7.1°C | +0.2°C |
| Avg Rain | 22 mm | 30 mm | 27 mm | 25 mm | 36 mm | +14 mm |
September temperatures in Merredin have stayed relatively stable across the record.
September has ranged from a record low of -0.2°C (2005) to a record high of 33.3°C (2023).
Rainfall in September is about average for rainfall, averaging 27 mm, with a wettest year of 59 mm.
A quieter season to visit Merredin
If your dates are flexible, the more temperate months of November and March tend to be the most comfortable for visiting Merredin. That said, September — with days averaging 20.8°C and nights around 6.8°C (mean 13.8°C) and low rainfall (27 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 | 19.5°C | 12.9°C | 6.3°C | 26.6°C | 3.3°C | 53 mm | 75% | 2.6 m/s | 5.7 |
| 2024 | 21.8°C | 14.5°C | 7.3°C | 28.7°C | 2.8°C | 14 mm | 67% | 2.8 m/s | 5.7 |
| 2023 🔥 | 23.8°C | 16.5°C | 9.2°C | 33.3°C | 1.8°C | 36 mm | 69% | 3 m/s | 5.4 |
| 2022 | 19.0°C | 12.9°C | 6.7°C | 25.7°C | 2.6°C | 36 mm | 75% | 2.7 m/s | 5 |
| 2021 | 19.9°C | 12.8°C | 5.8°C | 25.5°C | 0.9°C | 35 mm | 70% | 2.7 m/s | 5.5 |
| 2020 | 20.5°C | 13.9°C | 7.3°C | 29.3°C | 4.0°C | 41 mm | 72% | 3 m/s | 5.5 |
| 2019 | 24.0°C | 16.1°C | 8.1°C | 31.4°C | 1.1°C | 9 mm | 62% | 2.6 m/s | 5.9 |
| 2018 | 21.0°C | 13.7°C | 6.5°C | 29.8°C | 0.7°C | 12 mm | 67% | 2.7 m/s | 5.7 |
| 2017 | 20.9°C | 14.2°C | 7.6°C | 29.6°C | 1.6°C | 42 mm | 68% | 2.7 m/s | 5.1 |
| 2016 | 18.3°C | 11.7°C | 5.0°C | 24.3°C | 0.6°C | 18 mm | 69% | 2.8 m/s | 5.5 |
| 2015 | 21.9°C | 14.0°C | 6.0°C | 29.8°C | 0.6°C | 7 mm | 63% | 2.7 m/s | 5.7 |
| 2014 | 23.7°C | 16.3°C | 8.9°C | 31.2°C | 4.4°C | 27 mm | 67% | 3.1 m/s | 5.2 |
| 2013 🌧️ | 19.9°C | 13.9°C | 7.9°C | 24.6°C | 3.2°C | 59 mm | 74% | 3.3 m/s | 5.1 |
| 2012 | 21.9°C | 14.4°C | 6.9°C | 28.2°C | 0.9°C | 32 mm | 63% | 3.3 m/s | 5.6 |
| 2011 | 20.0°C | 13.2°C | 6.4°C | 25.0°C | 3.4°C | 36 mm | 71% | 2.7 m/s | 5.3 |
| 2010 | 21.3°C | 13.7°C | 6.1°C | 28.4°C | 2.1°C | 5 mm | 59% | 2.7 m/s | 5.7 |
| 2009 | 18.1°C | 11.7°C | 5.3°C | 24.5°C | 2.0°C | 31 mm | 74% | 3.2 m/s | 5.2 |
| 2008 | 20.3°C | 13.5°C | 6.7°C | 27.6°C | 0.2°C | 53 mm | 70% | 3.1 m/s | 5.1 |
| 2007 | 21.2°C | 14.1°C | 7.1°C | 29.1°C | 3.7°C | 23 mm | 71% | 3 m/s | 5.4 |
| 2006 | 21.4°C | 14.4°C | 7.3°C | 33.1°C | 2.4°C | 44 mm | 68% | 3.2 m/s | 5.2 |
| 2005 | 19.5°C | 12.7°C | 6.0°C | 28.5°C | -0.2°C | 30 mm | 70% | 3.3 m/s | 5.4 |
| 2004 | 20.8°C | 13.5°C | 6.2°C | 27.4°C | 0.5°C | 13 mm | 64% | 2.7 m/s | 5.2 |
| 2003 | 19.6°C | 13.1°C | 6.6°C | 29.6°C | 4.3°C | 26 mm | 72% | 3.2 m/s | 5 |
| 2002 | 21.5°C | 13.9°C | 6.3°C | 29.9°C | 0.4°C | 14 mm | 64% | 3.1 m/s | 5.5 |
| 2001 | 20.7°C | 13.8°C | 6.8°C | 31.5°C | 1.6°C | 29 mm | 71% | 3 m/s | 4.9 |
| 2000 | 22.6°C | 15.2°C | 7.7°C | 29.9°C | 3.8°C | 9 mm | 68% | 2.7 m/s | 5.5 |
| 1999 | 20.2°C | 13.5°C | 6.7°C | 28.0°C | 0.6°C | 38 mm | 73% | 3 m/s | 5.1 |
| 1998 | 19.5°C | 12.6°C | 5.8°C | 25.4°C | 1.0°C | 22 mm | 71% | 3.2 m/s | 5 |
| 1997 | 20.4°C | 13.8°C | 7.1°C | 27.0°C | 2.4°C | 33 mm | 73% | 2.5 m/s | 5 |
| 1996 | 19.8°C | 13.3°C | 6.9°C | 25.1°C | 3.2°C | 49 mm | 73% | 3.5 m/s | 5 |
| 1995 | 20.5°C | 14.0°C | 7.6°C | 25.9°C | 4.1°C | 29 mm | 72% | 2.5 m/s | 5.2 |
| 1994 | 22.9°C | 15.0°C | 7.1°C | 30.8°C | 0.4°C | 14 mm | 62% | 3.1 m/s | 5.8 |
| 1993 | 19.6°C | 12.8°C | 5.9°C | 26.1°C | 0.6°C | 24 mm | 70% | 2.8 m/s | 5.3 |
| 1992 ❄️ | 16.3°C | 11.1°C | 5.9°C | 24.0°C | 1.3°C | 48 mm | 80% | 3 m/s | 4.6 |
| 1991 | 21.1°C | 13.9°C | 6.7°C | 32.0°C | 1.5°C | 23 mm | 70% | 2.8 m/s | 5.5 |
| 1990 | 21.9°C | 14.1°C | 6.3°C | 30.9°C | 0.4°C | 21 mm | 63% | 2.6 m/s | 5.4 |
| 1989 | 21.1°C | 13.9°C | 6.8°C | 26.3°C | 2.2°C | 8 mm | 68% | 3 m/s | 5.6 |
| 1988 | 20.6°C | 13.8°C | 7.0°C | 28.7°C | 4.1°C | 20 mm | 72% | 3.1 m/s | 5.2 |
| 1987 | 22.6°C | 14.9°C | 7.2°C | 33.0°C | 2.1°C | 16 mm | 60% | 2.8 m/s | 5.6 |
| 1986 | 20.1°C | 13.4°C | 6.8°C | 26.2°C | 1.4°C | 21 mm | 72% | 2.6 m/s | 5.2 |
| 1985 | 22.1°C | 14.6°C | 7.0°C | 29.3°C | 2.0°C | 27 mm | 63% | 3 m/s | 5.4 |
| 1984 | 19.1°C | 12.4°C | 5.7°C | 24.0°C | 2.0°C | 25 mm | 68% | 3 m/s | 5.5 |
| 1983 | 21.8°C | 14.9°C | 8.1°C | 31.9°C | 5.3°C | 39 mm | 71% | 3.2 m/s | — |
| 1982 | 21.3°C | 13.9°C | 6.4°C | 30.9°C | 1.7°C | 33 mm | 65% | 2.8 m/s | — |
| 1981 | 21.8°C | 14.4°C | 7.1°C | 30.5°C | 2.3°C | 11 mm | 67% | 2.8 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 20.8°C with lows near 6.8°C (mean 13.8°C), based on 45 years of NASA POWER data.
September averages 27 mm of rainfall in Merredin, about average for rainfall. The wettest on record was 59 mm in 2013.
The hottest September reached 33.3°C in 2023. The coldest dipped to -0.2°C in 2005.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have fallen by about 0.1°C — but days and nights have moved in opposite directions. Overnight lows rose from 6.9°C to 7.1°C while daytime highs eased from 21.2°C to 20.8°C, narrowing the gap between day and night.
September is one of the cooler months of the year in Merredin and about average for rainfall, so plan for around 20.8°C daytime highs and 6.8°C at night.
Not quite — September is the 4th coolest month in Merredin, averaging 13.8°C.
For September in Merredin, pack warm layers and a jacket for chilly mornings, with typical highs of 20.8°C and lows of 6.8°C.
Relative humidity in September averages 69% — moderately humid.
Average wind speed in September is 2.9 m/s. The windiest September on record averaged 3.5 m/s (1996).
The wettest September on record was 2013 with 59 mm. On average, September sees 27 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 Merredin 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.
