September is one of the warmer months of the year in Conwy, with average highs near 15.8°C and lows around 12.7°C (mean 14.3°C). It is about average for rainfall, averaging 88 mm of rainfall and 84% relative humidity across the period.
September is one of the warmer months of the year in Conwy. Across 45 years of records, the warmest September in Conwy was 2023 — when the month averaged 16.4°C — while the coldest was 1986 at 12°C. Typical September days reach 15.8°C with nights near 12.7°C. The long-term trend is warming, about 0.3°C per decade.
September is about average for rainfall in Conwy, averaging 88 mm of rainfall. The wettest September on record was 2025 with 184 mm, while the driest was 1986 at 12 mm.
Relative humidity in Conwy during September averages 84%. The most humid September was 1998 at 88%, and the least humid was 1990 at 81%.
September receives about 2.9 kWh/m²/day of solar energy in Conwy. The sunniest Septembers were 1986 and 1991 at 3.4 kWh/m²/day, and the cloudiest were 1993 and 2000 at 2.5.
Average wind speed in Conwy during September is 5 m/s. The windiest Septembers were 1983 and 2004 at 6.2 m/s, while the calmest was 2014 at 3.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 13.7°C | 13.9°C | 14.6°C | 14.3°C | 15.1°C | +1.4°C |
| Avg High | 15.1°C | 15.4°C | 16.1°C | 15.8°C | 16.8°C | +1.7°C |
| Avg Low | 12.3°C | 12.3°C | 13.1°C | 12.8°C | 13.5°C | +1.2°C |
| Avg Rain | 77 mm | 78 mm | 86 mm | 94 mm | 113 mm | +36 mm |
September temperatures in Conwy have risen by about 1.2°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 8.4°C (1986) to a record high of 22.6°C (2023).
Rainfall in September is about average for rainfall, averaging 88 mm, with a wettest year of 184 mm.
One of the best times to visit Conwy
September is one of the best times to visit Conwy. Expect days averaging 15.8°C and nights around 12.7°C (mean 14.3°C) — warmer than Conwy's yearly average — with higher rainfall (88 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 🌧️ | 16.3°C | 14.6°C | 13.0°C | 18.9°C | 10.1°C | 184 mm | 83% | 5.4 m/s | 2.8 |
| 2024 | 15.7°C | 14.1°C | 12.6°C | 20.3°C | 10.7°C | 110 mm | 86% | 5 m/s | 2.7 |
| 2023 🔥 | 18.2°C | 16.4°C | 14.6°C | 22.6°C | 12.3°C | 132 mm | 86% | 4.7 m/s | 2.8 |
| 2022 | 16.8°C | 15.4°C | 13.9°C | 20.1°C | 11.9°C | 103 mm | 82% | 4.9 m/s | 3 |
| 2021 | 17.7°C | 16.0°C | 14.3°C | 22.4°C | 10.5°C | 80 mm | 86% | 3.9 m/s | 2.8 |
| 2020 | 16.0°C | 14.3°C | 12.6°C | 20.0°C | 9.5°C | 68 mm | 84% | 5.1 m/s | 3.1 |
| 2019 | 15.9°C | 14.6°C | 13.2°C | 19.1°C | 11.4°C | 134 mm | 84% | 5.1 m/s | 2.9 |
| 2018 | 15.4°C | 14.0°C | 12.6°C | 18.9°C | 9.4°C | 94 mm | 82% | 5.8 m/s | 2.8 |
| 2017 | 15.4°C | 14.0°C | 12.7°C | 18.2°C | 10.9°C | 145 mm | 86% | 5.3 m/s | 2.7 |
| 2016 | 17.0°C | 15.6°C | 14.2°C | 21.3°C | 11.8°C | 79 mm | 85% | 5.2 m/s | 2.9 |
| 2015 | 15.0°C | 13.3°C | 11.6°C | 18.0°C | 9.2°C | 57 mm | 83% | 4.3 m/s | 3.3 |
| 2014 | 16.7°C | 15.0°C | 13.4°C | 18.6°C | 12.2°C | 13 mm | 84% | 3.2 m/s | 3.1 |
| 2013 | 15.4°C | 13.8°C | 12.3°C | 19.3°C | 9.4°C | 72 mm | 85% | 4.9 m/s | 2.6 |
| 2012 | 14.7°C | 13.3°C | 11.9°C | 18.1°C | 9.3°C | 146 mm | 84% | 5.8 m/s | 2.8 |
| 2011 | 16.2°C | 14.7°C | 13.2°C | 20.0°C | 11.9°C | 95 mm | 85% | 6 m/s | 2.8 |
| 2010 | 15.8°C | 14.3°C | 12.9°C | 18.8°C | 9.6°C | 108 mm | 85% | 5.4 m/s | 2.8 |
| 2009 | 15.5°C | 14.2°C | 12.9°C | 18.7°C | 10.5°C | 51 mm | 85% | 5 m/s | 2.8 |
| 2008 | 15.5°C | 14.1°C | 12.6°C | 17.7°C | 10.4°C | 121 mm | 86% | 4.8 m/s | 2.6 |
| 2007 | 15.4°C | 14.2°C | 13.0°C | 17.4°C | 8.7°C | 84 mm | 86% | 5.4 m/s | 2.9 |
| 2006 | 17.8°C | 16.0°C | 14.3°C | 21.1°C | 12.0°C | 73 mm | 86% | 4.9 m/s | 3.1 |
| 2005 | 16.6°C | 15.0°C | 13.4°C | 20.9°C | 10.9°C | 85 mm | 85% | 5.1 m/s | 2.9 |
| 2004 | 16.1°C | 14.5°C | 13.0°C | 19.5°C | 11.2°C | 95 mm | 86% | 6.2 m/s | 3.1 |
| 2003 | 16.4°C | 14.8°C | 13.2°C | 19.6°C | 10.3°C | 101 mm | 83% | 3.9 m/s | 3 |
| 2002 | 16.1°C | 14.5°C | 13.0°C | 18.8°C | 11.1°C | 44 mm | 83% | 3.5 m/s | 3.1 |
| 2001 | 15.0°C | 13.7°C | 12.3°C | 17.6°C | 9.9°C | 73 mm | 86% | 5.5 m/s | 2.6 |
| 2000 | 16.3°C | 14.7°C | 13.2°C | 20.1°C | 10.7°C | 135 mm | 86% | 4.8 m/s | 2.5 |
| 1999 | 16.8°C | 15.1°C | 13.3°C | 21.0°C | 11.6°C | 116 mm | 86% | 4.5 m/s | 3 |
| 1998 | 15.9°C | 14.3°C | 12.8°C | 20.2°C | 10.1°C | 89 mm | 88% | 4.9 m/s | 3 |
| 1997 | 15.9°C | 14.3°C | 12.7°C | 18.2°C | 10.2°C | 44 mm | 84% | 5.4 m/s | 2.9 |
| 1996 | 15.8°C | 14.0°C | 12.3°C | 18.7°C | 10.2°C | 29 mm | 82% | 4.9 m/s | 3 |
| 1995 | 15.4°C | 14.1°C | 12.7°C | 18.5°C | 10.1°C | 92 mm | 83% | 4.7 m/s | 3 |
| 1994 | 14.0°C | 12.8°C | 11.5°C | 16.5°C | 9.8°C | 122 mm | 85% | 5.3 m/s | 2.8 |
| 1993 | 14.6°C | 13.0°C | 11.4°C | 17.5°C | 9.3°C | 93 mm | 83% | 5.1 m/s | 2.5 |
| 1992 | 14.7°C | 13.2°C | 11.7°C | 18.6°C | 10.2°C | 80 mm | 85% | 5.6 m/s | 3 |
| 1991 | 16.6°C | 14.6°C | 12.7°C | 20.6°C | 9.7°C | 46 mm | 81% | 4.7 m/s | 3.4 |
| 1990 | 14.7°C | 13.3°C | 12.0°C | 18.1°C | 9.8°C | 71 mm | 81% | 5.4 m/s | 2.8 |
| 1989 | 15.7°C | 14.3°C | 12.8°C | 18.2°C | 11.4°C | 24 mm | 83% | 4.8 m/s | 2.8 |
| 1988 | 14.4°C | 13.2°C | 12.0°C | 20.3°C | 8.7°C | 79 mm | 84% | 5.9 m/s | 2.6 |
| 1987 | 14.9°C | 13.6°C | 12.3°C | 18.0°C | 9.3°C | 85 mm | 83% | 5.3 m/s | 3.1 |
| 1986 ❄️ | 13.4°C | 12.0°C | 10.6°C | 16.4°C | 8.4°C | 12 mm | 81% | 4.3 m/s | 3.4 |
| 1985 | 15.6°C | 14.2°C | 12.7°C | 19.1°C | 10.7°C | 64 mm | 87% | 5.1 m/s | 2.7 |
| 1984 | 14.9°C | 13.8°C | 12.6°C | 18.5°C | 9.8°C | 130 mm | 82% | 5.5 m/s | 2.7 |
| 1983 | 15.1°C | 13.6°C | 12.2°C | 17.6°C | 10.4°C | 105 mm | 84% | 6.2 m/s | — |
| 1982 | 15.7°C | 14.0°C | 12.2°C | 20.5°C | 8.6°C | 81 mm | 85% | 4.8 m/s | — |
| 1981 | 16.2°C | 14.7°C | 13.1°C | 19.3°C | 11.4°C | 117 mm | 83% | 5.3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 15.8°C with lows near 12.7°C (mean 14.3°C), based on 45 years of NASA POWER data.
September averages 88 mm of rainfall in Conwy, about average for rainfall. The wettest on record was 184 mm in 2025.
The hottest September reached 22.6°C in 2023. The coldest dipped to 8.4°C in 1986.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.2°C. Daytime highs moved from 15.5°C to 16.9°C and overnight lows from 12.6°C to 13.7°C over the same span.
September is one of the warmer months of the year in Conwy and about average for rainfall, so plan for around 15.8°C daytime highs and 12.7°C at night.
Not quite — September is the 10th coolest month in Conwy, averaging 14.3°C.
For September in Conwy, pack light layers you can adjust through the day, with typical highs of 15.8°C and lows of 12.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 84% — quite humid.
Average wind speed in September is 5 m/s. The windiest September on record averaged 6.2 m/s (1983).
The wettest September on record was 2025 with 184 mm. On average, September sees 88 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 Conwy 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.
