Click on a day for an hourly weather forecast
The temperatures in Cardiff in September are usually low and can range between 12°C and 18°C.
You can expect about 3 to 8 days of rain in Cardiff during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Our weather forecast can give you a great sense of what weather to expect in Cardiff in September 2025.
If you’re planning to visit Cardiff in the near future, we highly recommend that you review the 14 day weather forecast for Cardiff before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 7° / 4° | 8 | 20 | 3 | 86 mm | Awful | Cardiff in January |
| February | 8° / 4° | 8 | 18 | 3 | 77 mm | Awful | Cardiff in February |
| March | 10° / 4° | 6 | 24 | 1 | 62 mm | Ok | Cardiff in March |
| April | 12° / 6° | 5 | 25 | 0 | 48 mm | Ok | Cardiff in April |
| May | 15° / 8° | 5 | 26 | 0 | 71 mm | Good | Cardiff in May |
| June | 18° / 11° | 5 | 25 | 0 | 72 mm | Good | Cardiff in June |
| July | 20° / 13° | 5 | 26 | 0 | 77 mm | Good | Cardiff in July |
| August | 19° / 13° | 6 | 25 | 0 | 85 mm | Good | Cardiff in August |
| September | 18° / 12° | 4 | 26 | 0 | 56 mm | Good | Cardiff in September |
| October | 14° / 10° | 7 | 24 | 0 | 99 mm | Ok | Cardiff in October |
| November | 11° / 7° | 8 | 22 | 0 | 101 mm | Bad | Cardiff in November |
| December | 9° / 5° | 9 | 21 | 2 | 105 mm | Awful | Cardiff in December |