Belfast weather in September
September in Belfast: nice, rainy, with clean air — an excellent time to visit.
#5 of 12 months in Belfast · #488 of 897 destinations to visit in September · comfort 81/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Traveller notes on Belfast in September
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Belfast climate normals — September
| Daytime high | 17°C / 62°F | 😎 nice |
|---|---|---|
| Nighttime low | 12°C / 54°F | |
| Rainfall | 90 mm / 3.5 in | 🌧 rainy |
| Rainy days | 14 days | |
| Humidity | 82% | 💦 very humid |
| Dew point | 12°C / 53°F | |
| Sunshine | 7.4 h/day | |
| Daylight | 12.7 h | |
| Wind | 20 km/h / 13 mph | |
| Air quality (US AQI) | 35 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Belfast in September — FAQ
- Is September a good time to visit Belfast?
- September in Belfast: nice, rainy, with clean air — an excellent time to visit. It ranks #5 of 12 months for Belfast on SeasonMap's comfort score (81/100).
- What is the weather like in Belfast in September?
- In September, Belfast averages a daily high of 16.5°C and a low of 12.1°C, with about 89.8 mm of rain over roughly 14 rainy days.
- What is the air quality in Belfast in September?
- Belfast has a mean US Air Quality Index of about 35 in September.