The temperatures in Carmarthen in September are usually low and can range between 11°C and 17°C.
You can expect about 3 to 8 days of rain in Carmarthen 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 Carmarthen in September 2025.
If you’re planning to visit Carmarthen in the near future, we highly recommend that you review the 14 day weather forecast for Carmarthen before you arrive.
Temperatures
17° / 11°
Rainy Days
6
Snowy Days
0
Dry Days
24
Rainfall
98
mm
Sun Hours
8.4
Hrs