September is one of the cooler months of the year in Westport, with average highs near 10.7°C and lows around 4.2°C (mean 7.5°C). It is about average for rainfall, averaging 161 mm of rainfall and 88% relative humidity across the period.
September is one of the cooler months of the year in Westport. Across 45 years of records, the warmest September in Westport was 1989 — when the month averaged 8.9°C — while the coldest was 1994 at 5.8°C. Typical September days reach 10.7°C with nights near 4.2°C. The long-term September temperature trend is broadly flat.
September is about average for rainfall in Westport, averaging 161 mm of rainfall. The wettest September on record was 1995 with 452 mm, while the driest was 1997 at 56 mm.
Relative humidity in Westport during September averages 88%. The most humid September was 2010 at 92%, and the least humid was 1997 at 83%.
September receives about 3.5 kWh/m²/day of solar energy in Westport. The sunniest Septembers were 1984 and 1985 at 4 kWh/m²/day, and the cloudiest was 2010 at 2.8.
Average wind speed in Westport during September is 0.4 m/s. The windiest Septembers were 1981 and 2010 at 0.5 m/s, while the calmest were 1984 and 1992 at 0.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 7.7°C | 7.1°C | 7.6°C | 7.4°C | 7.6°C | -0.1°C |
| Avg High | 11.1°C | 10.3°C | 11.0°C | 10.7°C | 10.6°C | -0.5°C |
| Avg Low | 4.3°C | 4.0°C | 4.3°C | 4.2°C | 4.7°C | +0.4°C |
| Avg Rain | 176 mm | 172 mm | 137 mm | 154 mm | 174 mm | -1 mm |
September temperatures in Westport have risen by about 0.3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -3.2°C (2007) to a record high of 17.4°C (1989).
Rainfall in September is about average for rainfall, averaging 161 mm, with a wettest year of 452 mm.
A quieter season to visit Westport
If your dates are flexible, the more temperate months of February and January tend to be the most comfortable for visiting Westport. That said, September — with days averaging 10.7°C and nights around 4.2°C (mean 7.5°C) and higher rainfall (161 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 | 10.0°C | 7.4°C | 4.7°C | 13.5°C | 0.5°C | 200 mm | 91% | 0.4 m/s | 3.6 |
| 2024 | 10.0°C | 7.4°C | 4.8°C | 14.7°C | 0.3°C | 193 mm | 91% | 0.4 m/s | 3.7 |
| 2023 | 11.7°C | 8.5°C | 5.4°C | 15.6°C | 0.8°C | 170 mm | 88% | 0.4 m/s | 3.5 |
| 2022 | 11.3°C | 7.9°C | 4.5°C | 15.8°C | -1.7°C | 116 mm | 87% | 0.4 m/s | 3.5 |
| 2021 | 10.2°C | 7.2°C | 4.2°C | 14.7°C | -0.1°C | 164 mm | 89% | 0.4 m/s | 3.6 |
| 2020 | 10.4°C | 7.4°C | 4.4°C | 13.4°C | -0.5°C | 202 mm | 90% | 0.4 m/s | 3.8 |
| 2019 | 10.6°C | 7.4°C | 4.3°C | 14.7°C | -1.1°C | 156 mm | 88% | 0.4 m/s | 3.5 |
| 2018 | 11.6°C | 7.8°C | 4.0°C | 15.6°C | -0.9°C | 63 mm | 86% | 0.4 m/s | 3.8 |
| 2017 | 10.6°C | 7.9°C | 5.1°C | 14.2°C | 0.0°C | 189 mm | 91% | 0.4 m/s | 3.4 |
| 2016 | 12.4°C | 8.6°C | 4.9°C | 15.8°C | -1.9°C | 122 mm | 86% | 0.4 m/s | 3.6 |
| 2015 | 10.0°C | 6.5°C | 3.0°C | 14.0°C | -1.3°C | 99 mm | 86% | 0.4 m/s | 3.9 |
| 2014 | 11.6°C | 7.8°C | 4.0°C | 15.4°C | -1.7°C | 151 mm | 87% | 0.4 m/s | 3.6 |
| 2013 | 10.7°C | 7.6°C | 4.6°C | 14.5°C | -0.3°C | 162 mm | 88% | 0.4 m/s | 3.3 |
| 2012 | 10.6°C | 7.5°C | 4.3°C | 15.8°C | -2.0°C | 221 mm | 89% | 0.4 m/s | 3.4 |
| 2011 | 9.9°C | 6.5°C | 3.2°C | 14.2°C | -0.9°C | 98 mm | 88% | 0.4 m/s | 3.5 |
| 2010 | 9.2°C | 6.7°C | 4.2°C | 14.2°C | -0.5°C | 283 mm | 92% | 0.5 m/s | 2.8 |
| 2009 | 11.1°C | 7.2°C | 3.3°C | 14.5°C | -3.0°C | 103 mm | 84% | 0.4 m/s | 3.9 |
| 2008 | 11.1°C | 7.7°C | 4.4°C | 15.7°C | -1.7°C | 118 mm | 89% | 0.4 m/s | 3.4 |
| 2007 | 11.7°C | 8.0°C | 4.4°C | 16.5°C | -3.2°C | 83 mm | 86% | 0.4 m/s | 3.7 |
| 2006 | 11.4°C | 8.4°C | 5.4°C | 14.1°C | 0.4°C | 110 mm | 89% | 0.4 m/s | 3.5 |
| 2005 | 11.7°C | 8.4°C | 5.1°C | 16.4°C | -1.6°C | 137 mm | 89% | 0.4 m/s | 3.4 |
| 2004 | 9.1°C | 6.1°C | 3.1°C | 13.5°C | -2.4°C | 201 mm | 90% | 0.4 m/s | 3.2 |
| 2003 | 9.9°C | 7.0°C | 4.0°C | 13.3°C | 0.1°C | 211 mm | 88% | 0.4 m/s | 3.3 |
| 2002 | 10.5°C | 7.5°C | 4.6°C | 13.1°C | -2.3°C | 206 mm | 90% | 0.4 m/s | 3.2 |
| 2001 | 12.2°C | 8.6°C | 5.0°C | 15.5°C | 1.8°C | 74 mm | 86% | 0.4 m/s | 3.8 |
| 2000 | 10.9°C | 7.5°C | 4.1°C | 13.7°C | -1.2°C | 126 mm | 87% | 0.4 m/s | 3.6 |
| 1999 | 11.7°C | 8.4°C | 5.2°C | 15.2°C | -0.4°C | 107 mm | 87% | 0.4 m/s | 3.6 |
| 1998 | 10.9°C | 8.0°C | 5.1°C | 15.6°C | -1.3°C | 135 mm | 88% | 0.4 m/s | 3.6 |
| 1997 | 10.8°C | 6.9°C | 3.0°C | 14.5°C | -2.0°C | 56 mm | 83% | 0.4 m/s | 3.4 |
| 1996 | 11.6°C | 8.6°C | 5.5°C | 16.7°C | -0.3°C | 218 mm | 89% | 0.4 m/s | 3.5 |
| 1995 🌧️ | 9.8°C | 7.1°C | 4.4°C | 13.9°C | -0.7°C | 452 mm | 91% | 0.4 m/s | 3.1 |
| 1994 ❄️ | 8.5°C | 5.8°C | 3.1°C | 11.1°C | -2.1°C | 198 mm | 90% | 0.4 m/s | 3.3 |
| 1993 | 9.6°C | 6.1°C | 2.7°C | 12.7°C | -2.5°C | 152 mm | 85% | 0.4 m/s | 3.6 |
| 1992 | 9.6°C | 6.0°C | 2.5°C | 12.6°C | -1.3°C | 107 mm | 85% | 0.3 m/s | 3.6 |
| 1991 | 10.4°C | 7.5°C | 4.6°C | 13.9°C | 0.9°C | 197 mm | 90% | 0.4 m/s | 3.4 |
| 1990 | 10.3°C | 6.9°C | 3.5°C | 13.3°C | -2.5°C | 95 mm | 87% | 0.4 m/s | 3.6 |
| 1989 🔥 | 13.3°C | 8.9°C | 4.4°C | 17.4°C | -2.8°C | 115 mm | 84% | 0.4 m/s | 3.9 |
| 1988 | 11.5°C | 8.6°C | 5.6°C | 15.6°C | 0.1°C | 233 mm | 90% | 0.4 m/s | 3.2 |
| 1987 | 10.2°C | 7.3°C | 4.4°C | 14.4°C | 0.7°C | 204 mm | 90% | 0.4 m/s | 3.2 |
| 1986 | 10.7°C | 7.3°C | 3.9°C | 13.6°C | 0.0°C | 179 mm | 86% | 0.4 m/s | 3.8 |
| 1985 | 11.4°C | 7.8°C | 4.3°C | 15.3°C | -0.9°C | 180 mm | 86% | 0.4 m/s | 4 |
| 1984 | 11.7°C | 7.7°C | 3.6°C | 14.8°C | -2.4°C | 120 mm | 85% | 0.3 m/s | 4 |
| 1983 | 10.2°C | 7.5°C | 4.9°C | 14.9°C | 1.0°C | 187 mm | 91% | 0.4 m/s | — |
| 1982 | 11.0°C | 7.4°C | 3.7°C | 13.4°C | -1.7°C | 165 mm | 86% | 0.4 m/s | — |
| 1981 | 9.5°C | 6.6°C | 3.8°C | 12.3°C | -2.3°C | 197 mm | 90% | 0.5 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 10.7°C with lows near 4.2°C (mean 7.5°C), based on 45 years of NASA POWER data.
September averages 161 mm of rainfall in Westport, about average for rainfall. The wettest on record was 452 mm in 1995.
The hottest September reached 17.4°C in 1989. The coldest dipped to -3.2°C in 2007.
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 4.1°C to 4.7°C while daytime highs eased from 10.8°C to 10.6°C, narrowing the gap between day and night.
September is one of the cooler months of the year in Westport and about average for rainfall, so plan for around 10.7°C daytime highs and 4.2°C at night.
Not quite — September is the 4th coolest month in Westport, averaging 7.5°C.
For September in Westport, pack warm layers and a jacket for chilly mornings, with typical highs of 10.7°C and lows of 4.2°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 88% — quite humid.
Average wind speed in September is 0.4 m/s. The windiest September on record averaged 0.5 m/s (1981).
The wettest September on record was 1995 with 452 mm. On average, September sees 161 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 Westport 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.
