Carmarthen Weather in September
What's the weather like in Carmarthen (Wales) in September 2025?
The climate in Carmarthen during September can be summarized as mild and wet.
September is in the fall / autumn in Carmarthen and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 17°C (62°F), whilst at night 10°C (49°F) is normal.
| Daytime temperature | 16.6°C 61.8°F |
|---|---|
| Nightly temperature | 9.5°C 49°F |
| Average temperature | 13°C 55.4°F |
| Daily sunshine | 4.7 hrs |
| Avg rainfall | 127 mm 5 ins |
| Rainy days | 16 days |
| Sea temperature | 15.9°C 60.6°F |
| Humidity | 89% |
| Windspeed | 19.4kph 12 mph |
On average September is the 5th wettest month of the year in Carmarthen with around 127mm 5 inches of rain making it a wet time to visit. This rainfall is typically spread over 16 days, although this may vary considerably.
On the flip side this corresponds to an average of 4.7 hours of sunshine per day.
September temperatures in Carmarthen
September rainfall
September hourly sunshine
The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Carmarthen in September 2025.
Other monthly averages
Best places to visit in September
Carmarthen weather stats
| Hottest month: | July | 18.6°C 65.5°F |
|---|---|---|
| Driest month: | April | 84mm 3.3ins |
| Sunniest month: | May | 6.9hrs |
| Coldest month: | February | 6.8°C 44.2°F |
| Wettest month: | December | 162mm 6.4ins |
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