September is one of the warmer months of the year in Ballymena, with average highs near 15.1°C and lows around 10.5°C (mean 12.8°C). It is about average for rainfall, averaging 96 mm of rainfall and 87% relative humidity across the period.
September is one of the warmer months of the year in Ballymena. Across 45 years of records, the warmest September in Ballymena was 2023 — when the month averaged 14.5°C — while the coldest was 1986 at 11.1°C. Typical September days reach 15.1°C with nights near 10.5°C. The long-term trend is warming, about 0.3°C per decade.
September is about average for rainfall in Ballymena, averaging 96 mm of rainfall. The wettest September on record was 1985 with 185 mm, while the driest was 2014 at 16 mm.
Relative humidity in Ballymena during September averages 87%. The most humid September was 1985 at 89%, and the least humid were 1986 and 1990 at 84%.
September receives about 2.7 kWh/m²/day of solar energy in Ballymena. The sunniest September was 1991 at 3.2 kWh/m²/day, and the cloudiest was 2021 at 2.3.
Average wind speed in Ballymena during September is 4.7 m/s. The windiest Septembers were 1983 and 2011 at 5.8 m/s, while the calmest was 2014 at 3.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 12.1°C | 12.6°C | 13.2°C | 12.8°C | 13.5°C | +1.4°C |
| Avg High | 14.4°C | 14.9°C | 15.4°C | 15.0°C | 15.9°C | +1.5°C |
| Avg Low | 9.8°C | 10.3°C | 10.9°C | 10.5°C | 11.1°C | +1.3°C |
| Avg Rain | 113 mm | 84 mm | 92 mm | 94 mm | 102 mm | -11 mm |
September temperatures in Ballymena have risen by about 1.3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 5.7°C (2007) to a record high of 23.2°C (2023).
Rainfall in September is about average for rainfall, averaging 96 mm, with a wettest year of 185 mm.
One of the best times to visit Ballymena
September is one of the best times to visit Ballymena. Expect days averaging 15.1°C and nights around 10.5°C (mean 12.8°C) — warmer than Ballymena's yearly average — with higher rainfall (96 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 | 15.3°C | 13.0°C | 10.6°C | 17.3°C | 8.2°C | 106 mm | 86% | 5.1 m/s | 2.6 |
| 2024 | 15.0°C | 12.6°C | 10.2°C | 19.8°C | 7.6°C | 60 mm | 86% | 4.6 m/s | 2.9 |
| 2023 🔥 | 17.1°C | 14.5°C | 12.0°C | 23.2°C | 9.2°C | 143 mm | 88% | 4.5 m/s | 2.8 |
| 2022 | 15.9°C | 13.8°C | 11.7°C | 18.6°C | 8.8°C | 145 mm | 85% | 4.5 m/s | 2.8 |
| 2021 | 17.0°C | 14.4°C | 11.8°C | 20.9°C | 8.6°C | 74 mm | 88% | 3.5 m/s | 2.3 |
| 2020 | 15.2°C | 12.9°C | 10.5°C | 19.7°C | 6.7°C | 85 mm | 87% | 4.6 m/s | 2.8 |
| 2019 | 15.3°C | 13.1°C | 11.0°C | 18.2°C | 9.2°C | 108 mm | 87% | 4.5 m/s | 2.8 |
| 2018 | 14.4°C | 12.0°C | 9.6°C | 19.0°C | 5.8°C | 83 mm | 85% | 5.3 m/s | 2.5 |
| 2017 | 14.7°C | 12.5°C | 10.4°C | 18.0°C | 7.9°C | 134 mm | 88% | 5.1 m/s | 2.5 |
| 2016 | 16.1°C | 13.7°C | 11.4°C | 20.3°C | 7.2°C | 98 mm | 88% | 5 m/s | 2.4 |
| 2015 | 14.3°C | 12.0°C | 9.7°C | 16.3°C | 7.9°C | 53 mm | 88% | 4.3 m/s | 2.8 |
| 2014 | 16.1°C | 13.6°C | 11.0°C | 19.1°C | 8.2°C | 16 mm | 88% | 3.1 m/s | 2.8 |
| 2013 | 14.9°C | 12.7°C | 10.5°C | 18.9°C | 7.8°C | 81 mm | 87% | 4.7 m/s | 2.6 |
| 2012 | 14.1°C | 11.9°C | 9.8°C | 18.5°C | 7.0°C | 112 mm | 86% | 5.5 m/s | 2.7 |
| 2011 | 15.2°C | 13.0°C | 10.7°C | 19.3°C | 8.2°C | 129 mm | 87% | 5.8 m/s | 2.6 |
| 2010 | 15.2°C | 13.2°C | 11.1°C | 18.4°C | 7.3°C | 131 mm | 87% | 4.9 m/s | 2.7 |
| 2009 | 15.1°C | 12.8°C | 10.5°C | 17.2°C | 7.7°C | 49 mm | 88% | 4.7 m/s | 2.8 |
| 2008 | 14.8°C | 12.7°C | 10.5°C | 17.2°C | 8.4°C | 116 mm | 88% | 4.2 m/s | 2.6 |
| 2007 | 15.0°C | 12.6°C | 10.2°C | 18.5°C | 5.7°C | 63 mm | 87% | 4.6 m/s | 2.7 |
| 2006 | 16.6°C | 14.3°C | 12.1°C | 20.0°C | 9.0°C | 142 mm | 89% | 4.7 m/s | 2.7 |
| 2005 | 15.9°C | 13.5°C | 11.2°C | 19.9°C | 7.5°C | 77 mm | 87% | 5.2 m/s | 2.6 |
| 2004 | 15.3°C | 13.3°C | 11.2°C | 19.6°C | 9.6°C | 117 mm | 88% | 5.7 m/s | 2.7 |
| 2003 | 15.7°C | 13.3°C | 10.9°C | 19.7°C | 7.7°C | 81 mm | 87% | 3.8 m/s | 2.5 |
| 2002 | 15.6°C | 13.3°C | 11.0°C | 17.9°C | 8.5°C | 54 mm | 88% | 3.5 m/s | 2.8 |
| 2001 | 14.8°C | 12.7°C | 10.6°C | 18.4°C | 7.4°C | 63 mm | 87% | 5 m/s | 2.6 |
| 2000 | 15.6°C | 13.3°C | 11.0°C | 19.0°C | 8.1°C | 155 mm | 88% | 4.3 m/s | 2.4 |
| 1999 | 15.9°C | 13.6°C | 11.2°C | 21.0°C | 7.6°C | 174 mm | 89% | 4.7 m/s | 2.4 |
| 1998 | 15.4°C | 13.3°C | 11.2°C | 19.5°C | 8.2°C | 79 mm | 89% | 4.5 m/s | 2.7 |
| 1997 | 15.2°C | 12.8°C | 10.3°C | 18.7°C | 8.1°C | 61 mm | 86% | 4.8 m/s | 2.9 |
| 1996 | 15.5°C | 12.9°C | 10.3°C | 19.3°C | 8.1°C | 41 mm | 87% | 4.4 m/s | 3 |
| 1995 | 15.0°C | 12.9°C | 10.7°C | 18.3°C | 7.8°C | 88 mm | 86% | 4.4 m/s | 2.8 |
| 1994 | 14.0°C | 11.9°C | 9.7°C | 18.1°C | 7.8°C | 74 mm | 86% | 4.2 m/s | 2.9 |
| 1993 | 14.1°C | 11.8°C | 9.6°C | 17.3°C | 6.7°C | 82 mm | 86% | 4.6 m/s | 2.5 |
| 1992 | 13.6°C | 11.4°C | 9.3°C | 17.6°C | 7.5°C | 117 mm | 86% | 4.8 m/s | 2.9 |
| 1991 | 15.7°C | 13.1°C | 10.5°C | 19.9°C | 6.6°C | 66 mm | 85% | 4.4 m/s | 3.2 |
| 1990 | 14.2°C | 12.0°C | 9.8°C | 19.6°C | 7.0°C | 56 mm | 84% | 4.9 m/s | 2.5 |
| 1989 | 14.9°C | 12.3°C | 9.8°C | 18.2°C | 7.7°C | 63 mm | 85% | 4.6 m/s | 2.5 |
| 1988 | 14.0°C | 11.9°C | 9.9°C | 18.1°C | 6.3°C | 109 mm | 87% | 5.4 m/s | 2.4 |
| 1987 | 14.0°C | 11.7°C | 9.4°C | 16.4°C | 6.5°C | 102 mm | 86% | 5.2 m/s | 2.8 |
| 1986 ❄️ | 13.6°C | 11.1°C | 8.6°C | 17.7°C | 5.8°C | 23 mm | 84% | 4.2 m/s | 2.9 |
| 1985 🌧️ | 15.1°C | 12.8°C | 10.6°C | 18.6°C | 7.3°C | 185 mm | 89% | 4.4 m/s | 2.5 |
| 1984 | 14.2°C | 12.2°C | 10.2°C | 19.2°C | 7.5°C | 122 mm | 84% | 4.7 m/s | 2.6 |
| 1983 | 14.3°C | 12.1°C | 9.9°C | 17.5°C | 6.7°C | 105 mm | 86% | 5.8 m/s | — |
| 1982 | 14.7°C | 12.0°C | 9.4°C | 19.0°C | 6.0°C | 128 mm | 86% | 5.1 m/s | — |
| 1981 | 15.2°C | 12.9°C | 10.6°C | 20.4°C | 8.6°C | 180 mm | 88% | 4.9 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 15.1°C with lows near 10.5°C (mean 12.8°C), based on 45 years of NASA POWER data.
September averages 96 mm of rainfall in Ballymena, about average for rainfall. The wettest on record was 185 mm in 1985.
The hottest September reached 23.2°C in 2023. The coldest dipped to 5.7°C in 2007.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.3°C. Daytime highs moved from 14.7°C to 16.1°C and overnight lows from 10.1°C to 11.3°C over the same span.
September is one of the warmer months of the year in Ballymena and about average for rainfall, so plan for around 15.1°C daytime highs and 10.5°C at night.
Not quite — September is the 10th coolest month in Ballymena, averaging 12.8°C.
For September in Ballymena, pack light layers you can adjust through the day, with typical highs of 15.1°C and lows of 10.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 87% — quite humid.
Average wind speed in September is 4.7 m/s. The windiest September on record averaged 5.8 m/s (1983).
The wettest September on record was 1985 with 185 mm. On average, September sees 96 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 Ballymena 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.
