September is one of the warmer months of the year in Plymouth, with average highs near 21.4°C and lows around 14.9°C (mean 18.2°C). It is about average for rainfall, averaging 100 mm of rainfall and 78% relative humidity across the period.
September is one of the warmer months of the year in Plymouth. Across 45 years of records, the warmest September in Plymouth was 2015 — when the month averaged 20.3°C — while the coldest were 1984 and 1986 at 16.5°C. Typical September days reach 21.4°C with nights near 14.9°C. The long-term trend is warming, about 0.6°C per decade.
September is about average for rainfall in Plymouth, averaging 100 mm of rainfall. The wettest September on record was 1996 with 272 mm, while the driest was 2014 at 33 mm.
Relative humidity in Plymouth during September averages 78%. The most humid September was 1996 at 86%, and the least humid was 1983 at 70%.
September receives about 4.3 kWh/m²/day of solar energy in Plymouth. The sunniest September was 2005 at 4.9 kWh/m²/day, and the cloudiest was 1996 at 3.4.
Average wind speed in Plymouth during September is 2.3 m/s. The windiest Septembers were 1991, 1995 and 2010 at 2.6 m/s, while the calmest was 2025 at 2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 17.3°C | 17.4°C | 18.3°C | 19.0°C | 19.2°C | +1.9°C |
| Avg High | 20.8°C | 20.6°C | 21.5°C | 22.2°C | 22.2°C | +1.4°C |
| Avg Low | 13.7°C | 14.2°C | 15.0°C | 15.8°C | 16.2°C | +2.5°C |
| Avg Rain | 78 mm | 119 mm | 96 mm | 96 mm | 113 mm | +35 mm |
September temperatures in Plymouth have risen by about 1.8°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 5.2°C (1992) to a record high of 32.1°C (2010).
Rainfall in September is about average for rainfall, averaging 100 mm, with a wettest year of 272 mm.
One of the best times to visit Plymouth
September is one of the best times to visit Plymouth. Expect days averaging 21.4°C and nights around 14.9°C (mean 18.2°C) — warmer than Plymouth's yearly average — with higher rainfall (100 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 22.3°C | 19.2°C | 16.1°C | 26.4°C | 13.6°C | 86 mm | 79% | 2 m/s | 4.4 |
| 2024 | 21.8°C | 18.8°C | 15.8°C | 26.7°C | 13.9°C | 81 mm | 78% | 2.3 m/s | 4.2 |
| 2023 | 22.3°C | 19.6°C | 17.0°C | 31.3°C | 12.6°C | 149 mm | 83% | 2.4 m/s | 4 |
| 2022 | 22.1°C | 18.9°C | 15.8°C | 27.9°C | 10.1°C | 102 mm | 77% | 2.3 m/s | 4.2 |
| 2021 | 22.3°C | 19.5°C | 16.7°C | 25.2°C | 11.6°C | 221 mm | 83% | 2.3 m/s | 4.3 |
| 2020 | 22.3°C | 19.2°C | 16.0°C | 29.5°C | 11.1°C | 37 mm | 73% | 2.5 m/s | 4.2 |
| 2019 | 21.7°C | 18.4°C | 15.2°C | 26.1°C | 10.3°C | 59 mm | 76% | 2.5 m/s | 4.8 |
| 2018 | 22.4°C | 19.7°C | 17.0°C | 31.7°C | 12.5°C | 149 mm | 81% | 2.4 m/s | 3.8 |
| 2017 | 21.9°C | 18.8°C | 15.6°C | 26.1°C | 11.6°C | 119 mm | 81% | 2.5 m/s | 4 |
| 2016 | 22.7°C | 19.7°C | 16.8°C | 32.0°C | 10.5°C | 76 mm | 76% | 2.5 m/s | 4 |
| 2015 🔥 | 23.8°C | 20.3°C | 16.8°C | 31.5°C | 12.1°C | 130 mm | 78% | 2.2 m/s | 4.8 |
| 2014 | 22.3°C | 18.8°C | 15.3°C | 29.0°C | 9.9°C | 33 mm | 75% | 2.1 m/s | 4.7 |
| 2013 | 21.0°C | 17.5°C | 13.9°C | 28.9°C | 9.3°C | 59 mm | 77% | 2.3 m/s | 4.6 |
| 2012 | 21.4°C | 18.2°C | 15.1°C | 26.0°C | 10.8°C | 128 mm | 78% | 2.4 m/s | 4.2 |
| 2011 | 21.7°C | 18.8°C | 16.0°C | 25.4°C | 11.0°C | 126 mm | 84% | 2.1 m/s | 4.2 |
| 2010 | 22.6°C | 19.3°C | 16.0°C | 32.1°C | 11.2°C | 85 mm | 78% | 2.6 m/s | 4.6 |
| 2009 | 20.1°C | 17.1°C | 14.1°C | 23.5°C | 9.9°C | 69 mm | 79% | 2.4 m/s | 4.5 |
| 2008 | 21.1°C | 18.3°C | 15.5°C | 28.0°C | 10.7°C | 209 mm | 81% | 2.4 m/s | 4.1 |
| 2007 | 22.7°C | 19.0°C | 15.3°C | 28.3°C | 11.0°C | 60 mm | 74% | 2.2 m/s | 4.8 |
| 2006 | 20.8°C | 17.7°C | 14.5°C | 25.0°C | 8.9°C | 68 mm | 80% | 2.4 m/s | 4.2 |
| 2005 | 22.7°C | 19.3°C | 15.8°C | 28.7°C | 10.0°C | 95 mm | 78% | 2.1 m/s | 4.9 |
| 2004 | 21.0°C | 17.8°C | 14.7°C | 25.6°C | 10.9°C | 149 mm | 81% | 2.3 m/s | 4.6 |
| 2003 | 21.4°C | 18.4°C | 15.4°C | 26.3°C | 11.5°C | 68 mm | 82% | 2.1 m/s | 4.3 |
| 2002 | 22.8°C | 19.3°C | 15.9°C | 30.9°C | 11.7°C | 117 mm | 78% | 2.4 m/s | 4.1 |
| 2001 | 21.6°C | 18.3°C | 14.9°C | 26.5°C | 11.1°C | 68 mm | 76% | 2.4 m/s | 4.6 |
| 2000 | 20.8°C | 17.4°C | 13.9°C | 27.0°C | 7.9°C | 60 mm | 77% | 2.3 m/s | 4.4 |
| 1999 | 22.0°C | 19.0°C | 15.9°C | 28.6°C | 10.8°C | 152 mm | 81% | 2.2 m/s | 4.3 |
| 1998 | 21.9°C | 18.2°C | 14.5°C | 26.2°C | 8.6°C | 79 mm | 77% | 2.1 m/s | 4.8 |
| 1997 | 20.8°C | 17.5°C | 14.2°C | 24.8°C | 8.5°C | 41 mm | 77% | 2.3 m/s | 4.1 |
| 1996 🌧️ | 19.7°C | 17.1°C | 14.5°C | 25.7°C | 9.5°C | 272 mm | 86% | 2.5 m/s | 3.4 |
| 1995 | 20.5°C | 17.2°C | 13.9°C | 29.0°C | 10.0°C | 77 mm | 72% | 2.6 m/s | 4.4 |
| 1994 | 19.9°C | 16.7°C | 13.5°C | 24.6°C | 10.5°C | 110 mm | 79% | 2.4 m/s | 4.2 |
| 1993 | 20.7°C | 17.6°C | 14.4°C | 26.1°C | 8.2°C | 110 mm | 79% | 2.5 m/s | 3.7 |
| 1992 | 20.0°C | 16.8°C | 13.6°C | 26.2°C | 5.2°C | 104 mm | 80% | 2.4 m/s | 4.1 |
| 1991 | 19.9°C | 16.7°C | 13.6°C | 27.8°C | 6.3°C | 174 mm | 77% | 2.6 m/s | 4.1 |
| 1990 | 20.9°C | 17.5°C | 14.1°C | 27.0°C | 8.3°C | 68 mm | 76% | 2.4 m/s | 4.2 |
| 1989 | 20.8°C | 17.6°C | 14.3°C | 28.5°C | 7.6°C | 109 mm | 78% | 2.3 m/s | 4.4 |
| 1988 | 20.8°C | 17.0°C | 13.3°C | 25.5°C | 9.7°C | 44 mm | 72% | 2.2 m/s | 4.5 |
| 1987 | 20.1°C | 17.1°C | 14.1°C | 25.9°C | 7.4°C | 175 mm | 81% | 2.4 m/s | 3.9 |
| 1986 | 20.1°C | 16.5°C | 12.9°C | 25.1°C | 8.8°C | 36 mm | 76% | 2.2 m/s | 4.3 |
| 1985 | 20.5°C | 17.2°C | 13.8°C | 26.5°C | 9.5°C | 64 mm | 81% | 2.2 m/s | 4.5 |
| 1984 ❄️ | 20.0°C | 16.5°C | 12.9°C | 25.6°C | 9.0°C | 53 mm | 72% | 2.2 m/s | 4.7 |
| 1983 | 23.8°C | 19.6°C | 15.3°C | 30.3°C | 10.7°C | 35 mm | 70% | 2.1 m/s | — |
| 1982 | 20.1°C | 16.9°C | 13.7°C | 25.1°C | 11.3°C | 92 mm | 81% | 2.1 m/s | — |
| 1981 | 20.6°C | 17.0°C | 13.4°C | 26.1°C | 6.3°C | 91 mm | 77% | 2.5 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 21.4°C with lows near 14.9°C (mean 18.2°C), based on 45 years of NASA POWER data.
September averages 100 mm of rainfall in Plymouth, about average for rainfall. The wettest on record was 272 mm in 1996.
The hottest September reached 32.1°C in 2010. The coldest dipped to 5.2°C in 1992.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.8°C. Daytime highs moved from 21°C to 22.2°C and overnight lows from 13.8°C to 16.3°C over the same span.
September is one of the warmer months of the year in Plymouth and about average for rainfall, so plan for around 21.4°C daytime highs and 14.9°C at night.
Not quite — September is the 10th coolest month in Plymouth, averaging 18.2°C.
For September in Plymouth, pack light layers you can adjust through the day, with typical highs of 21.4°C and lows of 14.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 78% — quite humid.
Average wind speed in September is 2.3 m/s. The windiest September on record averaged 2.6 m/s (1991).
The wettest September on record was 1996 with 272 mm. On average, September sees 100 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 Plymouth 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.
