Carmarthen is among the wettest of UK towns: 1,459 mm (57 in) of rain a year
Peak summer warmth arrives in July, with afternoons near 20.2°C (68°F). Winter and summer sit 18°C apart. Its January nights stay gentler than in 77% of UK towns. Picnics, hikes and garden evenings come into their own from June to September, with highs of 18–20°C.
Met Office 1991–2020 averages for the town itself.
A year in Carmarthen at a glance
Each month’s typical high and low, in °C.
What a year in Carmarthen feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,459 mm of rain a year
December is the wettest month and June the driest. About 45 days a year bring 10 mm (0.4 in) or more. 7th wettest of 23 Dyfed towns of 2,500+.
Rain by month
Millimetres
Sunshine by month
Hours of bright sunshine at Aberporth
44 air frosts and 8 days of 25°C a year
On about 44 nights a year the air drops below freezing; days that stay below freezing are rare. About 8 days a year reach 25°C (77°F).
Day counts are 1991–2020 averages from the Met Office’s 2 km grid. The Met Office calls a day of 25°C or more a summer day and a night below 0°C an air frost; ground frosts, on grass, come more often.
The Met Office station at Aberporth
Aberporth is 22 miles north-west of Carmarthen, 133 m (436 ft) above sea level. It is the nearest of the 37 long-running stations the Met Office publishes in full.
| Month | High | Low | Rain | Air frosts | Sun (hours) |
|---|---|---|---|---|---|
| January | 7.8°C | 3.4°C | 90 mm | 4.5 | 60 |
| February | 7.9°C | 3.3°C | 67 mm | 3.8 | 79 |
| March | 9.4°C | 4.2°C | 58 mm | 1.8 | 127 |
| April | 11.6°C | 5.7°C | 54 mm | 0.4 | 172 |
| May | 14.3°C | 8.2°C | 55 mm | 0.0 | 210 |
| June | 16.6°C | 10.7°C | 64 mm | 0.0 | 203 |
| July | 18.3°C | 12.5°C | 67 mm | 0.0 | 187 |
| August | 18.3°C | 12.7°C | 75 mm | 0.0 | 169 |
| September | 16.7°C | 11.2°C | 71 mm | 0.0 | 141 |
| October | 13.6°C | 8.9°C | 107 mm | 0.0 | 99 |
| November | 10.5°C | 6.2°C | 117 mm | 0.6 | 59 |
| December | 8.5°C | 4.1°C | 107 mm | 3.5 | 49 |
| Year | 12.8°C | 7.6°C | 931 mm | 15 | 1,554 |
Met Office historic station data, Aberporth, 1991–2020 months averaged (a month needs 20 of the 30 years; estimated values counted, missing months left out). Sunshine: Kipp & Zonen recorder.
How Carmarthen compares
Against the 2,537 towns and cities of 2,500 or more across the UK, each with its own Met Office averages, and its place among Dyfed towns that size.
Nearby towns’ climate
The nearest towns of 1,000+ within 12 miles: a hill, a valley or the sea can make a real difference over a few miles.
| Town | July high | January low | Rain a year |
|---|---|---|---|
| Carmarthen | 20.2°C | 2.2°C | 1,459 mm |
| Pontyberem 7.9 mi | 19.6°C 0.5°C cooler | 1.8°C about the same | 1,503 mm |
| Pontyates 7.9 mi | 19.6°C 0.5°C cooler | 2.2°C about the same | 1,490 mm |
| St Clears 8.3 mi | 20.8°C 0.6°C warmer | 2.2°C about the same | 1,337 mm |
| Kidwelly 8.4 mi | 20.0°C about the same | 2.6°C about the same | 1,268 mm |
| Carway 9.4 mi | 20.1°C about the same | 2.2°C about the same | 1,349 mm |
| Tumble 9.4 mi | 19.5°C 0.6°C cooler | 2.3°C about the same | 1,610 mm |
Carmarthen weather by month
Average daily high and low, mean temperature and rain, 1991–2020, for the town itself (the Met Office’s HadUK-Grid).
| Month | High | Low | Mean | Rain |
|---|---|---|---|---|
| January | 8.2°C 47°F | 2.2°C 36°F | 5.2°C | 139 mm 5.5 in |
| February | 8.2°C 47°F | 1.9°C 35°F | 5.1°C | 103 mm 4.1 in |
| March | 10.2°C 50°F | 2.7°C 37°F | 6.4°C | 95 mm 3.7 in |
| April | 13.2°C 56°F | 4.3°C 40°F | 8.6°C | 99 mm 3.9 in |
| May | 16.3°C 61°F | 6.9°C 44°F | 11.3°C | 107 mm 4.2 in |
| June | 18.7°C 66°F | 9.7°C 49°F | 14.0°C | 89 mm 3.5 in |
| July | 20.2°C 68°F | 11.5°C 53°F | 15.7°C | 117 mm 4.6 in |
| August | 19.8°C 68°F | 11.3°C 52°F | 15.5°C | 107 mm 4.2 in |
| September | 17.8°C 64°F | 9.2°C 49°F | 13.3°C | 99 mm 3.9 in |
| October | 14.3°C 58°F | 6.8°C 44°F | 10.5°C | 147 mm 5.8 in |
| November | 10.5°C 51°F | 4.0°C 39°F | 7.3°C | 152 mm 6.0 in |
| December | 8.4°C 47°F | 2.2°C 36°F | 5.3°C | 206 mm 8.1 in |
| Year | 13.8°C | 6.1°C | 9.9°C | 1,459 mm |
Where Carmarthen’s numbers come from
Averages over 30 years, not a forecast.
- Mean temperature, rain and day counts: HadUK-Grid 1991–2020 averages for the 1 Met Office 2 km grid square whose centre lies inside Carmarthen’s built-up area.
- Highs and lows: the Met Office publishes average daily maxima and minima on its 12 km grid; each is moved by the difference between the town’s 2 km mean temperature and the 12 km square’s, which carries the town’s own height and setting over.
- Weather station and sunshine: Met Office historic station data for Aberporth, 22 miles away, months of 1991–2020 averaged.
- Comparisons: every town and city of 2,500 or more across the UK, all four nations, read the same way.
Met Office HadUK-Grid · Met Office Climate Data Portal · Historic station data. Open Government Licence v3.0.
Questions about Carmarthen’s climate
How warm does Carmarthen get in summer?
July is the warmest month, with average highs of 20.2°C (68°F). About 8 days a year reach 25°C (77°F), fewer than 63% of UK towns.
How cold does Carmarthen get in winter?
February nights average 1.9°C (35°F). The air drops below freezing on about 44 nights a year, and about under 1 days a year stay below freezing all day.
How much rain does Carmarthen get?
About 1,459 mm (57 in) a year, more than 96% of UK towns. December is the wettest month (206 mm) and June the driest (89 mm).
How sunny is it?
The nearest Met Office station with a sunshine record, Aberporth (22 miles away), averages 1,554 hours of bright sunshine a year. Sunshine isn’t on the town grid, so this is the station’s figure.
Where do these figures come from?
The Met Office’s HadUK-Grid 1991–2020 averages, which turn thousands of weather stations into a map of the UK in 2 km squares; the page reads the squares inside Carmarthen. They are 30-year averages, not a forecast.
Contains Met Office data © Crown copyright 2026, Open Government Licence v3.0. HadUK-Grid 1991–2020 averages via the Met Office Climate Data Portal; station averages from Met Office historic station data. Today’s forecast for Carmarthen →
Contains public sector information licensed under the Open Government Licence v3.0. Contains HM Land Registry data © Crown copyright and database right 2026. Contains OS data © Crown copyright and database right 2026 (ONS boundaries). Northern Ireland: Source: NISRA; contains Land & Property Services data and Ordnance Survey of Northern Ireland information, © Crown copyright, licensed under the Open Government Licence v3.0. Scotland: contains National Records of Scotland data, Registers of Scotland data and SEPA data, © Crown copyright / © SEPA 2025, licensed under the Open Government Licence v3.0.