September is one of the warmer months of the year in Antrim, with average highs near 15.6°C and lows around 9.5°C (mean 12.6°C). It is about average for rainfall, averaging 88 mm of rainfall and 88% relative humidity across the period.
September is one of the warmer months of the year in Antrim. Across 45 years of records, the warmest Septembers in Antrim were 2021 and 2023 — when the month averaged 14.4°C — while the coldest was 1986 at 10.8°C. Typical September days reach 15.6°C with nights near 9.5°C. The long-term trend is warming, about 0.3°C per decade.
September is about average for rainfall in Antrim, averaging 88 mm of rainfall. The wettest September on record was 1981 with 167 mm, while the driest was 2014 at 12 mm.
Relative humidity in Antrim during September averages 88%. The most humid September was 1985 at 91%, and the least humid was 1986 at 85%.
September receives about 2.7 kWh/m²/day of solar energy in Antrim. The sunniest September was 1991 at 3.2 kWh/m²/day, and the cloudiest was 2021 at 2.3.
Average wind speed in Antrim during September is 3.8 m/s. The windiest September was 2011 at 4.8 m/s, while the calmest was 2014 at 2.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 12.0°C | 12.3°C | 13.0°C | 12.5°C | 13.3°C | +1.3°C |
| Avg High | 15.0°C | 15.4°C | 16.0°C | 15.6°C | 16.5°C | +1.5°C |
| Avg Low | 8.9°C | 9.2°C | 10.0°C | 9.5°C | 10.2°C | +1.3°C |
| Avg Rain | 100 mm | 77 mm | 81 mm | 87 mm | 101 mm | +0 mm |
September temperatures in Antrim have risen by about 1.1°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 3.4°C (2018) to a record high of 24.4°C (2023).
Rainfall in September is about average for rainfall, averaging 88 mm, with a wettest year of 167 mm.
One of the best times to visit Antrim
September is one of the best times to visit Antrim. Expect days averaging 15.6°C and nights around 9.5°C (mean 12.6°C) — warmer than Antrim'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 | 15.6°C | 12.5°C | 9.4°C | 17.6°C | 5.9°C | 108 mm | 88% | 4 m/s | 2.6 |
| 2024 | 15.5°C | 12.3°C | 9.1°C | 20.7°C | 4.7°C | 52 mm | 88% | 3.7 m/s | 2.9 |
| 2023 | 17.6°C | 14.4°C | 11.3°C | 24.4°C | 7.0°C | 148 mm | 90% | 3.6 m/s | 2.8 |
| 2022 | 16.5°C | 13.5°C | 10.5°C | 19.1°C | 6.8°C | 132 mm | 87% | 3.6 m/s | 2.8 |
| 2021 🔥 | 17.7°C | 14.4°C | 11.1°C | 21.7°C | 6.8°C | 68 mm | 90% | 2.9 m/s | 2.3 |
| 2020 | 15.9°C | 12.7°C | 9.5°C | 21.2°C | 4.6°C | 95 mm | 89% | 3.7 m/s | 2.8 |
| 2019 | 15.9°C | 12.8°C | 9.7°C | 19.1°C | 7.0°C | 112 mm | 88% | 3.6 m/s | 2.8 |
| 2018 | 15.0°C | 11.7°C | 8.4°C | 19.9°C | 3.4°C | 69 mm | 87% | 4.1 m/s | 2.5 |
| 2017 | 15.1°C | 12.2°C | 9.3°C | 18.9°C | 6.9°C | 125 mm | 89% | 4.1 m/s | 2.5 |
| 2016 | 16.5°C | 13.5°C | 10.5°C | 21.7°C | 4.9°C | 96 mm | 89% | 4.1 m/s | 2.4 |
| 2015 | 14.8°C | 11.6°C | 8.4°C | 16.8°C | 6.1°C | 53 mm | 89% | 3.4 m/s | 2.8 |
| 2014 | 16.8°C | 13.4°C | 10.0°C | 20.1°C | 6.3°C | 12 mm | 89% | 2.4 m/s | 2.8 |
| 2013 | 15.5°C | 12.5°C | 9.6°C | 20.0°C | 6.4°C | 68 mm | 88% | 3.7 m/s | 2.6 |
| 2012 | 14.6°C | 11.6°C | 8.6°C | 19.7°C | 4.8°C | 95 mm | 88% | 4.3 m/s | 2.7 |
| 2011 | 15.8°C | 12.8°C | 9.9°C | 20.1°C | 6.7°C | 109 mm | 88% | 4.8 m/s | 2.6 |
| 2010 | 15.6°C | 12.9°C | 10.2°C | 19.0°C | 6.0°C | 131 mm | 89% | 3.9 m/s | 2.7 |
| 2009 | 15.6°C | 12.5°C | 9.3°C | 17.7°C | 5.5°C | 44 mm | 89% | 3.7 m/s | 2.8 |
| 2008 | 15.3°C | 12.4°C | 9.4°C | 17.7°C | 6.5°C | 98 mm | 90% | 3.5 m/s | 2.6 |
| 2007 | 15.6°C | 12.4°C | 9.2°C | 19.1°C | 4.2°C | 53 mm | 89% | 3.6 m/s | 2.7 |
| 2006 | 17.1°C | 14.2°C | 11.3°C | 20.5°C | 7.1°C | 131 mm | 90% | 3.9 m/s | 2.7 |
| 2005 | 16.4°C | 13.3°C | 10.3°C | 20.7°C | 6.1°C | 71 mm | 89% | 4.2 m/s | 2.6 |
| 2004 | 15.9°C | 13.2°C | 10.5°C | 20.8°C | 8.2°C | 102 mm | 89% | 4.6 m/s | 2.7 |
| 2003 | 16.3°C | 13.0°C | 9.8°C | 20.3°C | 6.1°C | 67 mm | 88% | 3 m/s | 2.5 |
| 2002 | 16.1°C | 13.1°C | 10.1°C | 18.5°C | 6.9°C | 41 mm | 89% | 2.8 m/s | 2.8 |
| 2001 | 15.5°C | 12.5°C | 9.6°C | 19.2°C | 5.7°C | 62 mm | 89% | 3.9 m/s | 2.6 |
| 2000 | 16.1°C | 13.2°C | 10.2°C | 20.3°C | 6.5°C | 145 mm | 89% | 3.5 m/s | 2.4 |
| 1999 | 16.4°C | 13.4°C | 10.3°C | 22.0°C | 5.5°C | 160 mm | 90% | 3.8 m/s | 2.4 |
| 1998 | 15.9°C | 13.1°C | 10.3°C | 20.3°C | 6.9°C | 78 mm | 90% | 3.7 m/s | 2.7 |
| 1997 | 15.6°C | 12.5°C | 9.3°C | 19.6°C | 6.5°C | 57 mm | 88% | 3.8 m/s | 2.9 |
| 1996 | 16.1°C | 12.8°C | 9.4°C | 20.9°C | 6.8°C | 36 mm | 88% | 3.6 m/s | 3 |
| 1995 | 15.5°C | 12.5°C | 9.5°C | 19.5°C | 6.4°C | 74 mm | 88% | 3.5 m/s | 2.8 |
| 1994 | 14.5°C | 11.6°C | 8.7°C | 18.8°C | 6.5°C | 67 mm | 87% | 3.3 m/s | 2.9 |
| 1993 | 14.5°C | 11.6°C | 8.7°C | 19.3°C | 4.5°C | 97 mm | 88% | 3.8 m/s | 2.5 |
| 1992 | 14.1°C | 11.2°C | 8.2°C | 17.8°C | 4.3°C | 104 mm | 87% | 3.9 m/s | 2.9 |
| 1991 | 16.5°C | 13.0°C | 9.5°C | 21.6°C | 4.3°C | 57 mm | 86% | 3.6 m/s | 3.2 |
| 1990 | 14.8°C | 11.7°C | 8.5°C | 20.4°C | 4.8°C | 43 mm | 85% | 3.8 m/s | 2.5 |
| 1989 | 15.4°C | 12.2°C | 8.9°C | 18.6°C | 6.3°C | 61 mm | 87% | 3.7 m/s | 2.5 |
| 1988 | 14.6°C | 11.8°C | 9.0°C | 19.3°C | 3.5°C | 94 mm | 88% | 4.3 m/s | 2.4 |
| 1987 | 14.5°C | 11.5°C | 8.5°C | 17.1°C | 5.1°C | 100 mm | 87% | 4.1 m/s | 2.8 |
| 1986 ❄️ | 14.4°C | 10.8°C | 7.2°C | 18.6°C | 3.7°C | 15 mm | 85% | 3.2 m/s | 2.9 |
| 1985 | 15.9°C | 12.9°C | 9.9°C | 19.7°C | 5.3°C | 144 mm | 91% | 3.7 m/s | 2.5 |
| 1984 | 14.8°C | 12.0°C | 9.2°C | 19.9°C | 5.3°C | 111 mm | 86% | 3.8 m/s | 2.6 |
| 1983 | 14.7°C | 11.8°C | 9.0°C | 18.4°C | 4.7°C | 96 mm | 87% | 4.6 m/s | — |
| 1982 | 15.1°C | 11.8°C | 8.5°C | 20.0°C | 4.0°C | 113 mm | 88% | 4 m/s | — |
| 1981 🌧️ | 15.6°C | 12.8°C | 9.9°C | 20.9°C | 6.9°C | 167 mm | 89% | 4.1 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 15.6°C with lows near 9.5°C (mean 12.6°C), based on 45 years of NASA POWER data.
September averages 88 mm of rainfall in Antrim, about average for rainfall. The wettest on record was 167 mm in 1981.
The hottest September reached 24.4°C in 2023. The coldest dipped to 3.4°C in 2018.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.1°C. Daytime highs moved from 15.2°C to 16.6°C and overnight lows from 9.3°C to 10.3°C over the same span.
September is one of the warmer months of the year in Antrim and about average for rainfall, so plan for around 15.6°C daytime highs and 9.5°C at night.
Not quite — September is the 9th coolest month in Antrim, averaging 12.6°C.
For September in Antrim, pack light layers you can adjust through the day, with typical highs of 15.6°C and lows of 9.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 88% — quite humid.
Average wind speed in September is 3.8 m/s. The windiest September on record averaged 4.8 m/s (2011).
The wettest September on record was 1981 with 167 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 Antrim 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.
