September is one of the cooler months of the year in Whanganui, with average highs near 13.9°C and lows around 8.7°C (mean 11.3°C). It is about average for rainfall, averaging 90 mm of rainfall and 84% relative humidity across the period.
September is one of the cooler months of the year in Whanganui. Across 45 years of records, the warmest September in Whanganui was 2005 — when the month averaged 12.6°C — while the coldest was 1992 at 9.4°C. Typical September days reach 13.9°C with nights near 8.7°C. The long-term September temperature trend is broadly flat.
September is about average for rainfall in Whanganui, averaging 90 mm of rainfall. The wettest September on record was 2010 with 200 mm, while the driest was 2001 at 12 mm.
Relative humidity in Whanganui during September averages 84%. The most humid September was 1988 at 87%, and the least humid was 1985 at 81%.
September receives about 3.6 kWh/m²/day of solar energy in Whanganui. The sunniest September was 1985 at 4.2 kWh/m²/day, and the cloudiest was 2010 at 3.
Average wind speed in Whanganui during September is 4.9 m/s. The windiest September was 2010 at 6.5 m/s, while the calmest was 1989 at 3.6 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 11.4°C | 10.8°C | 11.5°C | 11.3°C | 11.5°C | +0.1°C |
| Avg High | 14.2°C | 13.4°C | 14.3°C | 13.8°C | 14.1°C | -0.1°C |
| Avg Low | 8.7°C | 8.2°C | 8.7°C | 8.9°C | 9.0°C | +0.3°C |
| Avg Rain | 78 mm | 93 mm | 66 mm | 101 mm | 126 mm | +47 mm |
September temperatures in Whanganui have risen by about 0.3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 3.3°C (1997) to a record high of 19.5°C (1988).
Rainfall in September is about average for rainfall, averaging 90 mm, with a wettest year of 200 mm.
A quieter season to visit Whanganui
If your dates are flexible, the more temperate months of February and January tend to be the most comfortable for visiting Whanganui. That said, September — with days averaging 13.9°C and nights around 8.7°C (mean 11.3°C) and higher rainfall (90 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 | 14.2°C | 11.8°C | 9.4°C | 17.2°C | 4.9°C | 100 mm | 82% | 6.1 m/s | 3.2 |
| 2024 | 14.1°C | 11.7°C | 9.4°C | 17.6°C | 5.8°C | 129 mm | 84% | 5.5 m/s | 3.6 |
| 2023 | 14.9°C | 12.2°C | 9.5°C | 18.2°C | 6.1°C | 140 mm | 84% | 5.4 m/s | 3.7 |
| 2022 | 14.1°C | 11.5°C | 8.8°C | 16.9°C | 4.7°C | 122 mm | 85% | 4.4 m/s | 3.3 |
| 2021 | 13.6°C | 10.9°C | 8.2°C | 16.4°C | 5.3°C | 125 mm | 83% | 5.3 m/s | 3.6 |
| 2020 | 13.7°C | 11.2°C | 8.8°C | 17.1°C | 3.4°C | 140 mm | 83% | 5.9 m/s | 3.7 |
| 2019 | 13.6°C | 11.2°C | 8.7°C | 17.6°C | 6.2°C | 87 mm | 84% | 5.3 m/s | 3.5 |
| 2018 | 13.6°C | 11.2°C | 8.7°C | 17.2°C | 6.2°C | 49 mm | 85% | 4.8 m/s | 3.9 |
| 2017 | 13.8°C | 11.6°C | 9.5°C | 17.0°C | 6.9°C | 128 mm | 85% | 5.2 m/s | 3.4 |
| 2016 | 14.2°C | 11.8°C | 9.4°C | 16.9°C | 5.8°C | 86 mm | 86% | 4.8 m/s | 3.1 |
| 2015 | 12.7°C | 10.3°C | 8.0°C | 16.1°C | 5.0°C | 116 mm | 84% | 5 m/s | 3.5 |
| 2014 | 14.3°C | 11.7°C | 9.0°C | 17.3°C | 5.8°C | 106 mm | 84% | 4.8 m/s | 3.7 |
| 2013 | 14.2°C | 11.7°C | 9.3°C | 16.9°C | 4.1°C | 113 mm | 83% | 5.8 m/s | 3.5 |
| 2012 | 14.1°C | 11.3°C | 8.5°C | 17.2°C | 4.6°C | 71 mm | 81% | 5.3 m/s | 3.4 |
| 2011 | 13.3°C | 10.6°C | 8.0°C | 16.5°C | 5.9°C | 59 mm | 82% | 4.6 m/s | 3.9 |
| 2010 🌧️ | 13.8°C | 11.7°C | 9.6°C | 17.6°C | 6.2°C | 200 mm | 84% | 6.5 m/s | 3 |
| 2009 | 14.0°C | 10.9°C | 7.9°C | 16.2°C | 3.5°C | 82 mm | 84% | 4.2 m/s | 3.8 |
| 2008 | 14.2°C | 11.4°C | 8.6°C | 17.2°C | 4.8°C | 52 mm | 85% | 4.6 m/s | 3.8 |
| 2007 | 14.2°C | 11.2°C | 8.2°C | 18.5°C | 3.7°C | 47 mm | 83% | 4.2 m/s | 3.7 |
| 2006 | 14.3°C | 11.8°C | 9.4°C | 17.1°C | 5.6°C | 34 mm | 86% | 5 m/s | 3.7 |
| 2005 🔥 | 15.6°C | 12.6°C | 9.6°C | 19.0°C | 6.4°C | 81 mm | 82% | 4.2 m/s | 3.8 |
| 2004 | 13.0°C | 10.2°C | 7.4°C | 15.5°C | 4.0°C | 87 mm | 82% | 5.4 m/s | 3.4 |
| 2003 | 14.3°C | 11.7°C | 9.1°C | 18.5°C | 6.0°C | 129 mm | 84% | 5.7 m/s | 3.2 |
| 2002 | 14.3°C | 11.8°C | 9.4°C | 16.5°C | 5.4°C | 82 mm | 82% | 6 m/s | 3.4 |
| 2001 | 14.9°C | 11.8°C | 8.7°C | 16.3°C | 5.8°C | 12 mm | 81% | 4.2 m/s | 3.8 |
| 2000 | 13.8°C | 11.2°C | 8.6°C | 17.2°C | 5.1°C | 59 mm | 82% | 4.9 m/s | 3.5 |
| 1999 | 14.6°C | 11.6°C | 8.6°C | 17.1°C | 3.8°C | 46 mm | 83% | 4.2 m/s | 3.8 |
| 1998 | 14.5°C | 11.8°C | 9.0°C | 17.7°C | 5.7°C | 53 mm | 83% | 4.9 m/s | 3.6 |
| 1997 | 13.4°C | 10.4°C | 7.3°C | 16.4°C | 3.3°C | 55 mm | 83% | 4.2 m/s | 3.5 |
| 1996 | 14.8°C | 12.0°C | 9.2°C | 18.8°C | 4.4°C | 87 mm | 85% | 4.4 m/s | 3.6 |
| 1995 | 13.8°C | 11.2°C | 8.6°C | 17.8°C | 4.7°C | 155 mm | 86% | 4.6 m/s | 3.4 |
| 1994 | 12.4°C | 10.1°C | 7.8°C | 15.3°C | 5.3°C | 152 mm | 85% | 4.9 m/s | 3.3 |
| 1993 | 12.2°C | 9.8°C | 7.3°C | 15.1°C | 4.4°C | 96 mm | 83% | 5 m/s | 3.5 |
| 1992 ❄️ | 11.6°C | 9.4°C | 7.2°C | 14.0°C | 4.5°C | 141 mm | 86% | 4.3 m/s | 3.4 |
| 1991 | 13.7°C | 11.3°C | 8.9°C | 17.0°C | 6.0°C | 86 mm | 85% | 4.6 m/s | 3.5 |
| 1990 | 12.9°C | 10.4°C | 7.8°C | 15.2°C | 5.0°C | 56 mm | 84% | 4.3 m/s | 3.8 |
| 1989 | 15.3°C | 12.1°C | 8.8°C | 19.0°C | 4.0°C | 35 mm | 83% | 3.6 m/s | 3.9 |
| 1988 | 14.6°C | 12.2°C | 9.8°C | 19.5°C | 5.3°C | 111 mm | 87% | 5.3 m/s | 3.2 |
| 1987 | 13.9°C | 11.4°C | 9.0°C | 17.1°C | 6.6°C | 84 mm | 82% | 5.3 m/s | 3.5 |
| 1986 | 13.2°C | 10.8°C | 8.3°C | 16.5°C | 4.0°C | 100 mm | 86% | 4.8 m/s | 3.7 |
| 1985 | 14.9°C | 11.6°C | 8.3°C | 18.2°C | 5.3°C | 48 mm | 81% | 4.5 m/s | 4.2 |
| 1984 | 14.1°C | 11.0°C | 8.0°C | 17.7°C | 5.3°C | 54 mm | 84% | 4.5 m/s | 3.8 |
| 1983 | 14.2°C | 11.7°C | 9.3°C | 17.1°C | 5.1°C | 112 mm | 84% | 5.5 m/s | — |
| 1982 | 13.7°C | 10.7°C | 7.8°C | 16.8°C | 4.0°C | 73 mm | 83% | 4.4 m/s | — |
| 1981 | 13.5°C | 11.3°C | 9.0°C | 16.2°C | 5.7°C | 89 mm | 84% | 6.2 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 13.9°C with lows near 8.7°C (mean 11.3°C), based on 45 years of NASA POWER data.
September averages 90 mm of rainfall in Whanganui, about average for rainfall. The wettest on record was 200 mm in 2010.
The hottest September reached 19.5°C in 1988. The coldest dipped to 3.3°C in 1997.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 0.3°C. Daytime highs moved from 14.1°C to 14.2°C and overnight lows from 8.5°C to 9.1°C over the same span.
September is one of the cooler months of the year in Whanganui and about average for rainfall, so plan for around 13.9°C daytime highs and 8.7°C at night.
Not quite — September is the 4th coolest month in Whanganui, averaging 11.3°C.
For September in Whanganui, pack light layers you can adjust through the day, with typical highs of 13.9°C and lows of 8.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 84% — quite humid.
Average wind speed in September is 4.9 m/s. The windiest September on record averaged 6.5 m/s (2010).
The wettest September on record was 2010 with 200 mm. On average, September sees 90 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 Whanganui 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.
