September is one of the cooler months of the year in Hamilton, with average highs near 15.1°C and lows around 5.2°C (mean 10.2°C). It is a relatively wet time of year, averaging 65 mm of rainfall and 82% relative humidity across the period.
September is one of the cooler months of the year in Hamilton. Across 45 years of records, the warmest September in Hamilton was 2023 — when the month averaged 12.4°C — while the coldest were 1984 and 1992 at 8.2°C. Typical September days reach 15.1°C with nights near 5.2°C. The long-term trend is warming, about 0.3°C per decade.
September is a relatively wet time of year in Hamilton, averaging 65 mm of rainfall. The wettest September on record was 2016 with 127 mm, while the driest was 2023 at 20 mm.
Relative humidity in Hamilton during September averages 82%. The most humid September was 1992 at 88%, and the least humid was 2006 at 72%.
September receives about 4 kWh/m²/day of solar energy in Hamilton. The sunniest September was 2023 at 4.7 kWh/m²/day, and the cloudiest was 2022 at 3.4.
Average wind speed in Hamilton during September is 3 m/s. The windiest September was 1996 at 3.8 m/s, while the calmest were 1997 and 2004 at 2.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 9.8°C | 9.8°C | 10.3°C | 10.2°C | 10.9°C | +1.1°C |
| Avg High | 14.9°C | 14.6°C | 15.3°C | 15.3°C | 15.9°C | +1°C |
| Avg Low | 4.9°C | 5.0°C | 5.2°C | 5.2°C | 5.9°C | +1°C |
| Avg Rain | 64 mm | 80 mm | 67 mm | 56 mm | 52 mm | -11 mm |
September temperatures in Hamilton have risen by about 1.3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -0.9°C (2003) to a record high of 27.9°C (2023).
Rainfall in September is a relatively wet time of year, averaging 65 mm, with a wettest year of 127 mm.
A quieter season to visit Hamilton
If your dates are flexible, the more temperate months of February and January tend to be the most comfortable for visiting Hamilton. That said, September — with days averaging 15.1°C and nights around 5.2°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 | 15.6°C | 10.7°C | 5.7°C | 22.7°C | 0.7°C | 41 mm | 79% | 3.4 m/s | 4 |
| 2024 | 15.9°C | 11.2°C | 6.5°C | 21.0°C | 1.5°C | 58 mm | 77% | 3.5 m/s | 3.8 |
| 2023 🔥 | 18.6°C | 12.4°C | 6.2°C | 27.9°C | 2.4°C | 20 mm | 73% | 2.8 m/s | 4.7 |
| 2022 | 14.3°C | 10.0°C | 5.8°C | 18.1°C | 1.7°C | 71 mm | 85% | 2.9 m/s | 3.4 |
| 2021 | 15.3°C | 10.4°C | 5.4°C | 22.6°C | 0.8°C | 50 mm | 81% | 3.1 m/s | 4.1 |
| 2020 | 15.6°C | 10.6°C | 5.5°C | 21.3°C | 0.5°C | 72 mm | 81% | 3.3 m/s | 4.1 |
| 2019 | 15.3°C | 9.8°C | 4.3°C | 21.7°C | 0.0°C | 44 mm | 79% | 2.7 m/s | 4.2 |
| 2018 | 15.0°C | 9.4°C | 3.8°C | 21.9°C | 0.2°C | 22 mm | 78% | 2.9 m/s | 4.5 |
| 2017 | 15.0°C | 10.2°C | 5.4°C | 22.8°C | 1.1°C | 53 mm | 79% | 3.5 m/s | 4 |
| 2016 🌧️ | 14.3°C | 9.7°C | 5.2°C | 19.5°C | 2.1°C | 127 mm | 86% | 2.6 m/s | 3.7 |
| 2015 | 16.5°C | 10.9°C | 5.4°C | 23.6°C | 1.8°C | 31 mm | 77% | 2.6 m/s | 4 |
| 2014 | 16.3°C | 10.9°C | 5.6°C | 23.9°C | 2.6°C | 35 mm | 81% | 2.7 m/s | 4.3 |
| 2013 | 16.3°C | 11.6°C | 7.0°C | 22.2°C | 2.7°C | 69 mm | 86% | 3.1 m/s | 3.7 |
| 2012 | 15.1°C | 10.3°C | 5.4°C | 20.8°C | 1.9°C | 59 mm | 82% | 3 m/s | 4.1 |
| 2011 | 15.3°C | 10.4°C | 5.5°C | 22.4°C | 0.9°C | 56 mm | 82% | 3 m/s | 4.1 |
| 2010 | 13.4°C | 9.1°C | 4.9°C | 16.4°C | 1.0°C | 68 mm | 87% | 2.7 m/s | 3.6 |
| 2009 | 15.2°C | 10.4°C | 5.6°C | 22.4°C | 2.2°C | 84 mm | 82% | 3.3 m/s | 3.8 |
| 2008 | 15.4°C | 10.0°C | 4.6°C | 23.8°C | 0.1°C | 53 mm | 80% | 3.1 m/s | 4.3 |
| 2007 | 15.6°C | 10.3°C | 5.0°C | 21.2°C | 0.8°C | 64 mm | 79% | 3.3 m/s | 4.2 |
| 2006 | 16.9°C | 11.0°C | 5.1°C | 24.7°C | 1.3°C | 57 mm | 72% | 3.2 m/s | 4.3 |
| 2005 | 15.7°C | 10.7°C | 5.7°C | 22.8°C | 0.2°C | 51 mm | 80% | 2.8 m/s | 3.9 |
| 2004 | 14.6°C | 9.9°C | 5.3°C | 23.2°C | 1.8°C | 52 mm | 86% | 2.4 m/s | 3.7 |
| 2003 | 13.7°C | 8.8°C | 3.9°C | 19.9°C | -0.9°C | 63 mm | 84% | 3.6 m/s | 4.1 |
| 2002 | 15.2°C | 10.0°C | 4.8°C | 23.2°C | 0.4°C | 59 mm | 76% | 3.6 m/s | 4 |
| 2001 | 16.4°C | 11.4°C | 6.3°C | 23.2°C | 2.2°C | 84 mm | 82% | 2.9 m/s | 3.9 |
| 2000 | 14.8°C | 10.3°C | 5.8°C | 20.7°C | 1.5°C | 106 mm | 87% | 3.5 m/s | 3.7 |
| 1999 | 17.1°C | 11.7°C | 6.3°C | 25.4°C | 2.2°C | 44 mm | 79% | 2.8 m/s | 4.3 |
| 1998 | 16.0°C | 10.9°C | 5.9°C | 21.7°C | 1.1°C | 91 mm | 83% | 3.1 m/s | 4 |
| 1997 | 15.2°C | 10.0°C | 4.8°C | 17.9°C | 2.3°C | 84 mm | 84% | 2.4 m/s | 4.2 |
| 1996 | 13.3°C | 9.0°C | 4.8°C | 21.6°C | 0.2°C | 126 mm | 84% | 3.8 m/s | 3.9 |
| 1995 | 14.4°C | 9.6°C | 4.8°C | 18.9°C | 0.6°C | 42 mm | 85% | 2.7 m/s | 4 |
| 1994 | 13.3°C | 8.5°C | 3.7°C | 18.8°C | 0.4°C | 49 mm | 80% | 2.8 m/s | 3.9 |
| 1993 | 15.4°C | 10.3°C | 5.1°C | 23.8°C | 0.1°C | 84 mm | 83% | 2.7 m/s | 4.1 |
| 1992 | 12.2°C | 8.2°C | 4.2°C | 15.4°C | 1.3°C | 116 mm | 88% | 2.5 m/s | 3.7 |
| 1991 | 14.1°C | 9.6°C | 5.1°C | 18.5°C | 1.3°C | 91 mm | 86% | 3 m/s | 4.1 |
| 1990 | 15.3°C | 10.4°C | 5.5°C | 22.2°C | 1.0°C | 69 mm | 82% | 3.1 m/s | 4.4 |
| 1989 | 14.9°C | 9.8°C | 4.8°C | 20.1°C | 1.8°C | 59 mm | 84% | 2.9 m/s | 4.4 |
| 1988 | 15.6°C | 10.7°C | 5.8°C | 20.4°C | 2.2°C | 76 mm | 83% | 3.1 m/s | 3.9 |
| 1987 | 15.6°C | 10.4°C | 5.2°C | 26.4°C | 1.0°C | 26 mm | 82% | 2.7 m/s | 4 |
| 1986 | 14.2°C | 9.6°C | 5.0°C | 20.3°C | 2.0°C | 72 mm | 86% | 3.1 m/s | 3.8 |
| 1985 | 14.5°C | 9.4°C | 4.4°C | 20.1°C | 1.7°C | 38 mm | 82% | 2.7 m/s | 4.5 |
| 1984 ❄️ | 12.7°C | 8.2°C | 3.8°C | 17.9°C | 0.0°C | 105 mm | 85% | 2.9 m/s | 3.9 |
| 1983 | 14.1°C | 9.5°C | 4.9°C | 21.5°C | -0.5°C | 113 mm | 85% | 3.4 m/s | — |
| 1982 | 16.3°C | 10.0°C | 3.8°C | 25.0°C | 0.4°C | 44 mm | 73% | 3 m/s | — |
| 1981 | 15.8°C | 10.9°C | 6.1°C | 23.4°C | 2.5°C | 38 mm | 85% | 3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 15.1°C with lows near 5.2°C (mean 10.2°C), based on 45 years of NASA POWER data.
September averages 65 mm of rainfall in Hamilton, a relatively wet time of year. The wettest on record was 127 mm in 2016.
The hottest September reached 27.9°C in 2023. The coldest dipped to -0.9°C in 2003.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.3°C. Daytime highs moved from 14.7°C to 15.9°C and overnight lows from 4.6°C to 5.9°C over the same span.
September is one of the cooler months of the year in Hamilton and a relatively wet time of year, so plan for around 15.1°C daytime highs and 5.2°C at night.
Not quite — September is the 4th coolest month in Hamilton, averaging 10.2°C.
For September in Hamilton, pack warm layers and a jacket for chilly mornings, with typical highs of 15.1°C and lows of 5.2°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 82% — quite humid.
Average wind speed in September is 3 m/s. The windiest September on record averaged 3.8 m/s (1996).
The wettest September on record was 2016 with 127 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 Hamilton 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.
