September is one of the cooler months of the year in Blenheim, with average highs near 12.3°C and lows around 4.4°C (mean 8.4°C). It is about average for rainfall, averaging 69 mm of rainfall and 86% relative humidity across the period.
September is one of the cooler months of the year in Blenheim. Across 45 years of records, the warmest September in Blenheim was 2001 — when the month averaged 9.7°C — while the coldest was 1992 at 6.3°C. Typical September days reach 12.3°C with nights near 4.4°C. The long-term September temperature trend is broadly flat.
September is about average for rainfall in Blenheim, averaging 69 mm of rainfall. The wettest September on record was 1995 with 140 mm, while the driest was 2001 at 8 mm.
Relative humidity in Blenheim during September averages 86%. The most humid September was 2022 at 89%, and the least humid was 2001 at 81%.
September receives about 3.8 kWh/m²/day of solar energy in Blenheim. The sunniest September was 2011 at 4.3 kWh/m²/day, and the cloudiest was 2010 at 3.3.
Average wind speed in Blenheim during September is 2.4 m/s. The windiest Septembers were 2010 and 2020 at 3.1 m/s, while the calmest were 1990 and 2011 at 1.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 8.4°C | 7.9°C | 8.7°C | 8.3°C | 8.5°C | +0.1°C |
| Avg High | 12.6°C | 11.8°C | 12.8°C | 12.2°C | 12.3°C | -0.3°C |
| Avg Low | 4.3°C | 4.0°C | 4.6°C | 4.5°C | 4.6°C | +0.3°C |
| Avg Rain | 64 mm | 83 mm | 49 mm | 76 mm | 78 mm | +13 mm |
September temperatures in Blenheim have risen by about 0.3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -1.5°C (1988) to a record high of 19.1°C (1983).
Rainfall in September is about average for rainfall, averaging 69 mm, with a wettest year of 140 mm.
A quieter season to visit Blenheim
If your dates are flexible, the more temperate months of February and January tend to be the most comfortable for visiting Blenheim. That said, September — with days averaging 12.3°C and nights around 4.4°C (mean 8.4°C) and moderate rainfall (69 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 | 12.5°C | 8.4°C | 4.4°C | 16.1°C | 0.6°C | 47 mm | 86% | 2.9 m/s | 4 |
| 2024 | 12.7°C | 8.5°C | 4.3°C | 15.8°C | -1.1°C | 66 mm | 85% | 2.4 m/s | 4 |
| 2023 | 12.9°C | 9.5°C | 6.1°C | 17.0°C | 2.1°C | 81 mm | 87% | 2.8 m/s | 3.7 |
| 2022 | 11.5°C | 8.2°C | 4.9°C | 16.3°C | -0.9°C | 90 mm | 89% | 2.3 m/s | 3.5 |
| 2021 | 11.6°C | 7.7°C | 3.8°C | 17.1°C | -0.4°C | 96 mm | 86% | 2.8 m/s | 3.9 |
| 2020 | 12.5°C | 8.4°C | 4.3°C | 15.0°C | -0.2°C | 86 mm | 85% | 3.1 m/s | 4.1 |
| 2019 | 12.2°C | 8.1°C | 4.0°C | 15.6°C | 0.5°C | 91 mm | 86% | 2.3 m/s | 3.8 |
| 2018 | 12.6°C | 8.6°C | 4.6°C | 17.6°C | 1.4°C | 36 mm | 86% | 2.3 m/s | 4.2 |
| 2017 | 12.3°C | 8.7°C | 5.0°C | 16.7°C | 0.7°C | 90 mm | 88% | 2.5 m/s | 3.5 |
| 2016 | 12.5°C | 9.2°C | 5.8°C | 15.9°C | 1.1°C | 76 mm | 88% | 2.4 m/s | 3.6 |
| 2015 | 11.1°C | 7.3°C | 3.5°C | 15.9°C | 0.6°C | 86 mm | 85% | 2.5 m/s | 4 |
| 2014 | 12.6°C | 8.7°C | 4.9°C | 18.6°C | -0.2°C | 65 mm | 85% | 2.3 m/s | 3.8 |
| 2013 | 12.4°C | 8.5°C | 4.7°C | 17.7°C | 0.6°C | 93 mm | 86% | 2.7 m/s | 3.7 |
| 2012 | 12.0°C | 8.2°C | 4.3°C | 17.2°C | 0.3°C | 66 mm | 85% | 2.6 m/s | 3.7 |
| 2011 | 12.2°C | 7.8°C | 3.3°C | 15.5°C | -0.2°C | 38 mm | 84% | 1.8 m/s | 4.3 |
| 2010 | 11.7°C | 8.2°C | 4.7°C | 16.5°C | -0.4°C | 116 mm | 86% | 3.1 m/s | 3.3 |
| 2009 | 12.3°C | 8.0°C | 3.7°C | 17.3°C | 0.4°C | 68 mm | 82% | 2.2 m/s | 3.9 |
| 2008 | 12.8°C | 8.8°C | 4.8°C | 17.1°C | 0.3°C | 65 mm | 87% | 2.2 m/s | 3.6 |
| 2007 | 12.7°C | 8.7°C | 4.7°C | 17.3°C | -0.6°C | 36 mm | 85% | 2.5 m/s | 3.9 |
| 2006 | 13.6°C | 9.3°C | 5.0°C | 17.0°C | 1.0°C | 15 mm | 86% | 2.3 m/s | 3.8 |
| 2005 | 13.6°C | 9.5°C | 5.3°C | 17.1°C | -0.2°C | 21 mm | 85% | 2.2 m/s | 3.7 |
| 2004 | 11.8°C | 7.5°C | 3.3°C | 16.5°C | 0.0°C | 84 mm | 85% | 2.6 m/s | 3.7 |
| 2003 | 12.0°C | 8.1°C | 4.3°C | 16.7°C | 1.1°C | 100 mm | 85% | 3 m/s | 3.6 |
| 2002 | 13.1°C | 8.9°C | 4.7°C | 18.0°C | 0.2°C | 44 mm | 83% | 2.9 m/s | 3.6 |
| 2001 🔥 | 14.2°C | 9.7°C | 5.2°C | 17.9°C | 1.9°C | 8 mm | 81% | 1.9 m/s | 4 |
| 2000 | 12.1°C | 8.3°C | 4.6°C | 16.8°C | 0.1°C | 48 mm | 85% | 2.4 m/s | 3.6 |
| 1999 | 13.2°C | 9.1°C | 4.9°C | 18.8°C | 0.1°C | 25 mm | 84% | 2.1 m/s | 3.9 |
| 1998 | 13.5°C | 9.0°C | 4.6°C | 17.0°C | 0.5°C | 53 mm | 84% | 2.3 m/s | 4 |
| 1997 | 10.8°C | 7.1°C | 3.4°C | 15.1°C | 0.1°C | 50 mm | 85% | 1.9 m/s | 3.7 |
| 1996 | 13.1°C | 9.3°C | 5.6°C | 17.8°C | 1.5°C | 87 mm | 88% | 2.2 m/s | 3.6 |
| 1995 🌧️ | 11.6°C | 7.9°C | 4.3°C | 15.3°C | 0.3°C | 140 mm | 87% | 2.5 m/s | 3.4 |
| 1994 | 11.1°C | 7.1°C | 3.1°C | 13.1°C | -0.7°C | 103 mm | 85% | 2 m/s | 3.7 |
| 1993 | 10.7°C | 6.8°C | 2.9°C | 15.3°C | -0.7°C | 56 mm | 84% | 2.3 m/s | 3.9 |
| 1992 ❄️ | 9.8°C | 6.3°C | 2.9°C | 12.7°C | -0.8°C | 131 mm | 87% | 2 m/s | 3.9 |
| 1991 | 12.1°C | 8.6°C | 5.1°C | 14.1°C | 1.7°C | 111 mm | 88% | 2.1 m/s | 3.8 |
| 1990 | 12.3°C | 7.9°C | 3.5°C | 15.6°C | -0.2°C | 76 mm | 84% | 1.8 m/s | 4.2 |
| 1989 | 12.5°C | 9.0°C | 5.6°C | 17.9°C | -0.7°C | 73 mm | 88% | 1.9 m/s | 3.8 |
| 1988 | 13.7°C | 9.5°C | 5.3°C | 17.8°C | -1.5°C | 56 mm | 86% | 2.4 m/s | 3.7 |
| 1987 | 13.0°C | 8.7°C | 4.3°C | 18.9°C | 0.2°C | 54 mm | 85% | 2.1 m/s | 3.8 |
| 1986 | 12.1°C | 7.8°C | 3.5°C | 16.6°C | 0.0°C | 73 mm | 86% | 2.2 m/s | 4.1 |
| 1985 | 12.3°C | 8.2°C | 4.1°C | 14.9°C | -1.4°C | 68 mm | 85% | 2.2 m/s | 4.2 |
| 1984 | 11.8°C | 8.1°C | 4.5°C | 15.2°C | -0.1°C | 39 mm | 87% | 2.4 m/s | 3.9 |
| 1983 | 12.7°C | 8.6°C | 4.5°C | 19.1°C | 1.0°C | 86 mm | 86% | 2.4 m/s | — |
| 1982 | 12.3°C | 8.1°C | 4.0°C | 16.4°C | 0.2°C | 85 mm | 84% | 2.1 m/s | — |
| 1981 | 12.6°C | 7.9°C | 3.1°C | 16.7°C | -0.7°C | 46 mm | 84% | 2.4 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 12.3°C with lows near 4.4°C (mean 8.4°C), based on 45 years of NASA POWER data.
September averages 69 mm of rainfall in Blenheim, about average for rainfall. The wettest on record was 140 mm in 1995.
The hottest September reached 19.1°C in 1983. The coldest dipped to -1.5°C in 1988.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 0.3°C — but days and nights have moved in opposite directions. Overnight lows rose from 4°C to 4.7°C while daytime highs eased from 12.3°C to 12.2°C, narrowing the gap between day and night.
September is one of the cooler months of the year in Blenheim and about average for rainfall, so plan for around 12.3°C daytime highs and 4.4°C at night.
Not quite — September is the 4th coolest month in Blenheim, averaging 8.4°C.
For September in Blenheim, pack warm layers and a jacket for chilly mornings, with typical highs of 12.3°C and lows of 4.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 86% — quite humid.
Average wind speed in September is 2.4 m/s. The windiest September on record averaged 3.1 m/s (2010).
The wettest September on record was 1995 with 140 mm. On average, September sees 69 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 Blenheim 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.
