Carmarthen weather forecast
UK towns · Carmarthenshire, Wales · 51.86°N 4.31°W
Carmarthen, in Carmarthenshire, Wales, has its warmest weather in August, when daytime temperatures average 19.1°C, while January nights are the coldest at around 2.6°C. The town sees roughly 1663mm of rain a year; December is normally the wettest month and April the driest. Figures are averaged from 2020–2024 observations.
Climate averages
| Month | Avg high | Avg low | Rain | Rain days |
|---|---|---|---|---|
| Jan | 7.6° | 2.6° | 145mm | 14 |
| Feb | 8.9° | 3.8° | 176mm | 17 |
| Mar | 10° | 3.8° | 148mm | 16 |
| Apr | 12.6° | 4.8° | 77mm | 11 |
| May | 15.6° | 8.1° | 102mm | 14 |
| Jun | 18.1° | 10.7° | 82mm | 14 |
| Jul | 18.8° | 12.2° | 126mm | 16 |
| Aug | 19.1° | 12.9° | 127mm | 17 |
| Sep | 17.6° | 11.4° | 150mm | 14 |
| Oct | 14.1° | 9.2° | 198mm | 21 |
| Nov | 10.9° | 6.2° | 132mm | 16 |
| Dec | 8.6° | 4.4° | 200mm | 20 |
Seasons in Carmarthen
Spring (March–May). Daytime highs in Carmarthen climb from 10°C in March to 15.6°C by May, while nights ease from 3.8°C to 8.1°C. The season brings around 327mm of rain in total.
Summer (June–August). The warmest stretch of the year: afternoons average 18.7°C, peaking in August at 19.1°C. June is usually the driest of the summer months (82mm over ~14 rainy days). Around the June solstice, Carmarthen gets roughly 16.5 hours of daylight.
Autumn (September–November). Daytime temperatures fall from 17.6°C in September to 10.9°C by November, with around 480mm of rain across the season.
Winter (December–February). Nights average 3.6°C, with January the coldest month (average low 2.6°C, daytime high 7.6°C). Expect about 51 days with measurable rain over the three months, and only around 7.5 hours of daylight in mid-December.
How Carmarthen compares
| Carmarthen | UK town average | |
|---|---|---|
| Annual rainfall | 1663mm | 1054mm |
| Rainy days per year | 190 | 167 |
| Summer daytime high | 18.7°C | 19.7°C |
| Winter night low | 3.6°C | 3.4°C |
Carmarthen is about 58% wetter than the average for the 121 UK towns tracked on this site (1054mm), based on 2020–2024 monthly normals.
Carmarthen weather FAQs
What is the warmest month in Carmarthen?
August is typically the warmest month in Carmarthen, with average daytime highs of 19.1°C. Summer afternoons (June–August) average around 18.7°C.
What is the wettest month in Carmarthen?
December is usually the wettest month, with around 200mm of rain over roughly 20 rainy days. April is typically the driest (77mm).
How much does it rain in Carmarthen per year?
Carmarthen receives roughly 1663mm of precipitation per year, spread over about 190 days with at least 1mm of rain (based on 2020–2024 observations).
How cold are winters in Carmarthen?
Winter nights (December–February) in Carmarthen average around 3.6°C, with January typically the coldest month (average low 2.6°C).
When is the best time to visit Carmarthen for good weather?
Late spring and summer offer the most reliable weather in Carmarthen. June is typically the driest of the warm months (82mm of rain), while August is the warmest, averaging 19.1°C by day — and near the June solstice there are around 16 hours of daylight to enjoy.
How does Carmarthen's weather compare with the rest of the UK?
Carmarthen receives 1663mm of rain a year, about 58% wetter than the average for the 121 UK towns tracked on this site (1054mm). Summer daytime highs average 18.7°C against a UK-town average of 19.7°C, and winter nights average 3.6°C versus 3.4°C.
Is it going to rain in Carmarthen?
For up-to-the-minute rain tracking, check the live rain radar — as a long-term guide, Carmarthen averages 190 rainy days a year, with December the wettest month (200mm) and April the driest (77mm).
What is the 7-day forecast for Carmarthen?
See the live hourly and 7-day forecast for day-by-day temperatures and rain chance. The figures on this page are long-term climate averages from 2020–2024, not the live forecast.