Cardiff weather in September
September in Cardiff: nice, rainy, with clean air — an excellent time to visit.
#5 of 12 months in Cardiff · #465 of 897 destinations to visit in September · comfort 82/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Traveller notes on Cardiff in September
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Cardiff climate normals — September
| Daytime high | 18°C / 65°F | 😎 nice |
|---|---|---|
| Nighttime low | 13°C / 55°F | |
| Rainfall | 92 mm / 3.6 in | 🌧 rainy |
| Rainy days | 10 days | |
| Humidity | 82% | 💦 very humid |
| Dew point | 13°C / 55°F | |
| Sunshine | 8 h/day | |
| Daylight | 12.6 h | |
| Wind | 21 km/h / 13 mph | |
| Air quality (US AQI) | 38 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Cardiff in September — FAQ
- Is September a good time to visit Cardiff?
- September in Cardiff: nice, rainy, with clean air — an excellent time to visit. It ranks #5 of 12 months for Cardiff on SeasonMap's comfort score (82/100).
- What is the weather like in Cardiff in September?
- In September, Cardiff averages a daily high of 18.3°C and a low of 12.6°C, with about 92.2 mm of rain over roughly 10 rainy days.
- What is the air quality in Cardiff in September?
- Cardiff has a mean US Air Quality Index of about 38 in September.