September is one of the cooler months of the year in Northam, with average highs near 20.1°C and lows around 6.9°C (mean 13.5°C). It is about average for rainfall, averaging 42 mm of rainfall and 75% relative humidity across the period.
September is one of the cooler months of the year in Northam. Across 45 years of records, the warmest September in Northam was 2023 — when the month averaged 16.3°C — while the coldest was 1992 at 11°C. Typical September days reach 20.1°C with nights near 6.9°C. The long-term September temperature trend is broadly flat.
September is about average for rainfall in Northam, averaging 42 mm of rainfall. The wettest September on record was 2013 with 87 mm, while the driest was 2010 at 10 mm.
Relative humidity in Northam during September averages 75%. The most humid September was 1992 at 84%, and the least humid was 2010 at 62%.
September receives about 5.1 kWh/m²/day of solar energy in Northam. The sunniest Septembers were 2015 and 2019 at 5.7 kWh/m²/day, and the cloudiest was 2001 at 4.5.
Average wind speed in Northam during September is 2.8 m/s. The windiest Septembers were 1996 and 2013 at 3.3 m/s, while the calmest were 1986 and 1995 at 2.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 13.7°C | 13.0°C | 13.1°C | 13.9°C | 14.0°C | +0.3°C |
| Avg High | 20.4°C | 19.4°C | 19.4°C | 20.8°C | 20.6°C | +0.2°C |
| Avg Low | 7.0°C | 6.7°C | 6.8°C | 7.0°C | 7.4°C | +0.4°C |
| Avg Rain | 37 mm | 49 mm | 44 mm | 35 mm | 48 mm | +11 mm |
September temperatures in Northam have risen by about 0.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 0.1°C (1993) to a record high of 34.9°C (2023).
Rainfall in September is about average for rainfall, averaging 42 mm, with a wettest year of 87 mm.
A quieter season to visit Northam
If your dates are flexible, the more temperate months of November and March tend to be the most comfortable for visiting Northam. That said, September — with days averaging 20.1°C and nights around 6.9°C (mean 13.5°C) and moderate rainfall (42 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 | 13.2°C | 6.8°C | 27.0°C | 3.2°C | 73 mm | 79% | 2.5 m/s | 5.4 |
| 2024 | 21.6°C | 14.6°C | 7.7°C | 29.3°C | 5.3°C | 18 mm | 72% | 2.8 m/s | 5.6 |
| 2023 🔥 | 23.0°C | 16.3°C | 9.6°C | 34.9°C | 2.4°C | 52 mm | 74% | 2.9 m/s | 5 |
| 2022 | 19.1°C | 13.0°C | 6.9°C | 25.2°C | 4.9°C | 46 mm | 79% | 2.6 m/s | 4.9 |
| 2021 | 19.9°C | 13.0°C | 6.1°C | 26.9°C | 2.5°C | 43 mm | 74% | 2.6 m/s | 5.4 |
| 2020 | 20.4°C | 13.9°C | 7.5°C | 28.5°C | 3.8°C | 56 mm | 76% | 2.9 m/s | 5.2 |
| 2019 | 23.6°C | 15.8°C | 8.0°C | 30.5°C | 0.9°C | 13 mm | 68% | 2.5 m/s | 5.7 |
| 2018 | 20.3°C | 13.3°C | 6.4°C | 28.5°C | 1.0°C | 12 mm | 75% | 2.5 m/s | 5.4 |
| 2017 | 20.2°C | 13.9°C | 7.6°C | 29.1°C | 2.1°C | 44 mm | 74% | 2.6 m/s | 4.9 |
| 2016 | 17.9°C | 11.4°C | 4.9°C | 23.6°C | 1.6°C | 29 mm | 75% | 2.6 m/s | 5 |
| 2015 | 22.2°C | 14.2°C | 6.2°C | 29.9°C | 1.2°C | 12 mm | 66% | 2.6 m/s | 5.7 |
| 2014 | 22.6°C | 15.7°C | 8.8°C | 31.2°C | 4.5°C | 41 mm | 74% | 2.8 m/s | 4.9 |
| 2013 🌧️ | 19.0°C | 13.6°C | 8.3°C | 22.7°C | 4.0°C | 87 mm | 80% | 3.3 m/s | 4.7 |
| 2012 | 21.2°C | 14.0°C | 6.9°C | 27.9°C | 1.1°C | 51 mm | 69% | 3.1 m/s | 5.3 |
| 2011 | 19.4°C | 13.1°C | 6.7°C | 24.3°C | 3.6°C | 56 mm | 76% | 2.7 m/s | 4.9 |
| 2010 | 21.6°C | 14.0°C | 6.5°C | 29.0°C | 2.4°C | 10 mm | 62% | 2.6 m/s | 5.6 |
| 2009 | 17.3°C | 11.5°C | 5.7°C | 24.4°C | 2.5°C | 55 mm | 80% | 3.1 m/s | 4.6 |
| 2008 | 19.6°C | 13.4°C | 7.3°C | 26.3°C | 0.5°C | 55 mm | 75% | 3 m/s | 4.8 |
| 2007 | 19.6°C | 13.2°C | 6.9°C | 26.7°C | 3.9°C | 47 mm | 79% | 2.8 m/s | 5 |
| 2006 | 20.5°C | 14.0°C | 7.5°C | 32.4°C | 1.5°C | 48 mm | 75% | 3 m/s | 5 |
| 2005 | 18.5°C | 12.4°C | 6.3°C | 26.2°C | 0.6°C | 53 mm | 77% | 3.2 m/s | 5 |
| 2004 | 19.9°C | 12.8°C | 5.8°C | 25.3°C | 0.5°C | 22 mm | 72% | 2.5 m/s | 5.1 |
| 2003 | 18.7°C | 12.8°C | 7.0°C | 28.2°C | 4.5°C | 53 mm | 78% | 3 m/s | 5 |
| 2002 | 19.9°C | 13.2°C | 6.5°C | 26.7°C | 0.4°C | 31 mm | 73% | 2.8 m/s | 5.1 |
| 2001 | 19.4°C | 13.1°C | 6.7°C | 29.3°C | 1.1°C | 52 mm | 78% | 2.7 m/s | 4.5 |
| 2000 | 21.0°C | 14.4°C | 7.9°C | 28.3°C | 5.2°C | 20 mm | 78% | 2.5 m/s | 5.1 |
| 1999 | 19.4°C | 13.0°C | 6.7°C | 26.7°C | 1.5°C | 72 mm | 79% | 2.8 m/s | 4.9 |
| 1998 | 18.6°C | 12.3°C | 6.0°C | 24.1°C | 1.4°C | 48 mm | 76% | 3.1 m/s | 4.9 |
| 1997 | 19.7°C | 13.5°C | 7.2°C | 25.1°C | 3.1°C | 44 mm | 79% | 2.5 m/s | 4.8 |
| 1996 | 18.6°C | 13.0°C | 7.5°C | 22.9°C | 2.9°C | 71 mm | 80% | 3.3 m/s | 4.9 |
| 1995 | 19.5°C | 13.5°C | 7.5°C | 25.7°C | 5.1°C | 41 mm | 79% | 2.4 m/s | 5 |
| 1994 | 22.0°C | 14.5°C | 6.9°C | 30.6°C | 0.6°C | 25 mm | 69% | 3 m/s | 5.6 |
| 1993 | 18.8°C | 12.4°C | 6.0°C | 25.6°C | 0.1°C | 54 mm | 76% | 2.7 m/s | 5 |
| 1992 ❄️ | 16.2°C | 11.0°C | 5.9°C | 24.5°C | 1.0°C | 57 mm | 84% | 2.9 m/s | 4.6 |
| 1991 | 19.5°C | 13.1°C | 6.7°C | 28.7°C | 0.6°C | 44 mm | 79% | 2.6 m/s | 5.2 |
| 1990 | 21.2°C | 13.7°C | 6.2°C | 30.3°C | 0.7°C | 32 mm | 71% | 2.5 m/s | 5.1 |
| 1989 | 20.2°C | 13.8°C | 7.5°C | 26.1°C | 2.6°C | 27 mm | 75% | 2.8 m/s | 5.1 |
| 1988 | 19.8°C | 13.7°C | 7.5°C | 27.9°C | 4.5°C | 44 mm | 78% | 2.9 m/s | 4.8 |
| 1987 | 22.1°C | 14.7°C | 7.3°C | 31.7°C | 1.8°C | 27 mm | 69% | 2.7 m/s | 5.5 |
| 1986 | 19.8°C | 13.3°C | 6.8°C | 26.8°C | 1.6°C | 25 mm | 77% | 2.4 m/s | 4.8 |
| 1985 | 21.3°C | 14.0°C | 6.7°C | 28.8°C | 2.1°C | 36 mm | 70% | 2.8 m/s | 5.1 |
| 1984 | 18.9°C | 12.4°C | 5.9°C | 23.8°C | 2.8°C | 46 mm | 73% | 2.9 m/s | 5.4 |
| 1983 | 20.6°C | 14.3°C | 8.1°C | 29.0°C | 4.7°C | 61 mm | 79% | 3 m/s | — |
| 1982 | 20.4°C | 13.4°C | 6.5°C | 31.0°C | 1.6°C | 47 mm | 72% | 2.7 m/s | — |
| 1981 | 20.4°C | 13.7°C | 7.1°C | 27.4°C | 2.3°C | 24 mm | 76% | 2.7 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 20.1°C with lows near 6.9°C (mean 13.5°C), based on 45 years of NASA POWER data.
September averages 42 mm of rainfall in Northam, about average for rainfall. The wettest on record was 87 mm in 2013.
The hottest September reached 34.9°C in 2023. The coldest dipped to 0.1°C in 1993.
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 20.3°C to 20.6°C and overnight lows from 6.9°C to 7.4°C over the same span.
September is one of the cooler months of the year in Northam and about average for rainfall, so plan for around 20.1°C daytime highs and 6.9°C at night.
Not quite — September is the 4th coolest month in Northam, averaging 13.5°C.
For September in Northam, pack warm layers and a jacket for chilly mornings, with typical highs of 20.1°C and lows of 6.9°C.
Relative humidity in September averages 75% — quite humid.
Average wind speed in September is 2.8 m/s. The windiest September on record averaged 3.3 m/s (1996).
The wettest September on record was 2013 with 87 mm. On average, September sees 42 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 Northam 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.
