December is one of the cooler months of the year in Llanelli, with average highs near 9.2°C and lows around 6.7°C (mean 8°C). It is a relatively wet time of year, averaging 139 mm of rainfall and 88% relative humidity across the period.
December is one of the cooler months of the year in Llanelli. Across 45 years of records, the warmest December in Llanelli was 2015 — when the month averaged 11.1°C — while the coldest was 2010 at 4°C. Typical December days reach 9.2°C with nights near 6.7°C. The long-term trend is warming, about 0.4°C per decade.
December is a relatively wet time of year in Llanelli, averaging 139 mm of rainfall. The wettest December on record was 2020 with 278 mm, while the driest was 1991 at 41 mm.
Relative humidity in Llanelli during December averages 88%. The most humid December was 1987 at 92%, and the least humid was 2014 at 84%.
December receives about 0.6 kWh/m²/day of solar energy in Llanelli. The sunniest Decembers were 2008, 2010 and 2014, among others at 0.7 kWh/m²/day, and the cloudiest was 2015 at 0.4.
Average wind speed in Llanelli during December is 6.3 m/s. The windiest December was 2015 at 8 m/s, while the calmest was 2016 at 4.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 7.8°C | 7.3°C | 7.8°C | 8.5°C | 8.7°C | +0.9°C |
| Avg High | 9.1°C | 8.7°C | 9.0°C | 9.6°C | 9.7°C | +0.6°C |
| Avg Low | 6.5°C | 6.0°C | 6.6°C | 7.3°C | 7.6°C | +1.1°C |
| Avg Rain | 126 mm | 125 mm | 114 mm | 154 mm | 198 mm | +73 mm |
December temperatures in Llanelli have risen by about 1.3°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -1.3°C (1996) to a record high of 14.1°C (1985).
Rainfall in December is a relatively wet time of year, averaging 139 mm, with a wettest year of 278 mm.
A quieter season to visit Llanelli
If your dates are flexible, the more temperate months of August and July tend to be the most comfortable for visiting Llanelli. That said, December — with days averaging 9.2°C and nights around 6.7°C (mean 8°C) and higher rainfall (139 mm) — can still be rewarding for travellers who don't mind the cooler conditions, and often means fewer crowds.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 9.9°C | 8.9°C | 7.9°C | 13.9°C | 3.3°C | 220 mm | 88% | 6.5 m/s | — |
| 2024 | 10.1°C | 9.0°C | 7.8°C | 13.2°C | 5.3°C | 132 mm | 89% | 6.1 m/s | 0.5 |
| 2023 | 10.6°C | 9.7°C | 8.7°C | 12.6°C | 2.7°C | 262 mm | 88% | 6.9 m/s | 0.6 |
| 2022 | 8.3°C | 7.2°C | 6.1°C | 13.0°C | 1.8°C | 134 mm | 88% | 5.4 m/s | 0.6 |
| 2021 | 10.1°C | 9.0°C | 7.9°C | 12.4°C | 5.2°C | 163 mm | 90% | 6.2 m/s | 0.6 |
| 2020 🌧️ | 9.3°C | 8.1°C | 7.0°C | 12.7°C | 3.8°C | 278 mm | 88% | 6.3 m/s | 0.6 |
| 2019 | 9.7°C | 8.6°C | 7.5°C | 12.5°C | 4.6°C | 198 mm | 87% | 6.2 m/s | 0.6 |
| 2018 | 10.6°C | 9.6°C | 8.6°C | 13.0°C | 4.4°C | 226 mm | 90% | 6.2 m/s | 0.5 |
| 2017 | 9.3°C | 8.0°C | 6.7°C | 12.8°C | 3.1°C | 180 mm | 88% | 6.2 m/s | 0.6 |
| 2016 | 10.1°C | 9.0°C | 7.9°C | 12.5°C | 4.1°C | 61 mm | 90% | 4.7 m/s | 0.6 |
| 2015 🔥 | 12.3°C | 11.1°C | 10.0°C | 13.4°C | 7.4°C | 270 mm | 89% | 8 m/s | 0.4 |
| 2014 | 9.7°C | 8.4°C | 7.1°C | 12.0°C | 3.4°C | 95 mm | 84% | 6.6 m/s | 0.7 |
| 2013 | 10.4°C | 9.1°C | 7.8°C | 12.5°C | 6.4°C | 104 mm | 84% | 6.9 m/s | 0.6 |
| 2012 | 9.2°C | 7.9°C | 6.7°C | 11.6°C | 3.0°C | 213 mm | 87% | 6.4 m/s | 0.6 |
| 2011 | 10.1°C | 8.9°C | 7.6°C | 12.6°C | 4.5°C | 150 mm | 84% | 7.5 m/s | 0.5 |
| 2010 ❄️ | 5.1°C | 4.0°C | 2.9°C | 9.4°C | 0.2°C | 41 mm | 87% | 4.8 m/s | 0.7 |
| 2009 | 8.0°C | 6.7°C | 5.4°C | 12.1°C | 1.4°C | 118 mm | 86% | 5.8 m/s | 0.6 |
| 2008 | 8.0°C | 6.8°C | 5.6°C | 11.1°C | 1.8°C | 77 mm | 88% | 5.5 m/s | 0.7 |
| 2007 | 9.5°C | 8.3°C | 7.2°C | 13.5°C | 3.5°C | 121 mm | 87% | 7.1 m/s | 0.6 |
| 2006 | 10.2°C | 9.1°C | 8.0°C | 13.3°C | 3.4°C | 139 mm | 86% | 7 m/s | 0.6 |
| 2005 | 9.0°C | 7.8°C | 6.6°C | 11.3°C | 1.2°C | 92 mm | 87% | 5.4 m/s | 0.6 |
| 2004 | 9.9°C | 8.8°C | 7.7°C | 11.8°C | 4.0°C | 95 mm | 88% | 5.6 m/s | 0.6 |
| 2003 | 9.4°C | 8.0°C | 6.6°C | 12.3°C | 2.9°C | 131 mm | 88% | 6.1 m/s | 0.6 |
| 2002 | 8.7°C | 7.7°C | 6.6°C | 12.3°C | 2.1°C | 145 mm | 91% | 6.2 m/s | 0.5 |
| 2001 | 8.3°C | 6.9°C | 5.4°C | 13.2°C | 2.0°C | 57 mm | 86% | 6 m/s | 0.7 |
| 2000 | 9.0°C | 8.1°C | 7.1°C | 12.7°C | 2.3°C | 166 mm | 89% | 7.1 m/s | 0.6 |
| 1999 | 9.3°C | 8.0°C | 6.8°C | 12.2°C | 2.2°C | 215 mm | 85% | 7.7 m/s | 0.5 |
| 1998 | 9.9°C | 8.4°C | 7.0°C | 12.4°C | 2.2°C | 126 mm | 88% | 6 m/s | 0.5 |
| 1997 | 9.8°C | 8.5°C | 7.3°C | 13.0°C | 1.1°C | 121 mm | 88% | 6.5 m/s | 0.5 |
| 1996 | 6.7°C | 5.3°C | 3.9°C | 11.8°C | -1.3°C | 44 mm | 88% | 5.7 m/s | 0.6 |
| 1995 | 6.9°C | 5.5°C | 4.1°C | 12.4°C | 0.5°C | 116 mm | 90% | 5.8 m/s | 0.5 |
| 1994 | 10.6°C | 9.3°C | 8.0°C | 13.1°C | 3.5°C | 167 mm | 87% | 7.3 m/s | 0.6 |
| 1993 | 9.1°C | 7.7°C | 6.2°C | 11.8°C | 2.6°C | 202 mm | 86% | 7.7 m/s | 0.6 |
| 1992 | 7.9°C | 6.6°C | 5.4°C | 12.2°C | 1.6°C | 112 mm | 88% | 5.7 m/s | 0.6 |
| 1991 | 8.5°C | 7.2°C | 6.0°C | 11.6°C | 1.6°C | 41 mm | 88% | 5.6 m/s | 0.6 |
| 1990 | 7.9°C | 6.5°C | 5.2°C | 11.4°C | 2.3°C | 106 mm | 85% | 6.3 m/s | 0.5 |
| 1989 | 8.8°C | 7.5°C | 6.1°C | 12.5°C | 2.5°C | 159 mm | 90% | 6.5 m/s | 0.6 |
| 1988 | 10.3°C | 9.1°C | 8.0°C | 11.8°C | 3.5°C | 45 mm | 89% | 5.3 m/s | 0.5 |
| 1987 | 8.6°C | 7.6°C | 6.6°C | 12.0°C | 2.3°C | 84 mm | 92% | 6.8 m/s | 0.5 |
| 1986 | 9.7°C | 8.2°C | 6.8°C | 12.8°C | 3.5°C | 165 mm | 86% | 7.2 m/s | 0.6 |
| 1985 | 9.8°C | 8.7°C | 7.7°C | 14.1°C | 1.1°C | 153 mm | 88% | 6 m/s | 0.5 |
| 1984 | 9.5°C | 8.1°C | 6.8°C | 11.4°C | 3.8°C | 145 mm | 88% | 5.3 m/s | 0.7 |
| 1983 | 9.8°C | 8.6°C | 7.3°C | 12.0°C | 4.6°C | 126 mm | 88% | 6.3 m/s | — |
| 1982 | 8.4°C | 7.1°C | 5.8°C | 12.3°C | 2.9°C | 134 mm | 87% | 6.3 m/s | — |
| 1981 | 6.6°C | 5.2°C | 3.7°C | 10.6°C | 0.1°C | 120 mm | 86% | 5.8 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 9.2°C with lows near 6.7°C (mean 8°C), based on 45 years of NASA POWER data.
December averages 139 mm of rainfall in Llanelli, a relatively wet time of year. The wettest on record was 278 mm in 2020.
The hottest December reached 14.1°C in 1985. The coldest dipped to -1.3°C in 1996.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.3°C. Daytime highs moved from 8.8°C to 9.8°C and overnight lows from 6.3°C to 7.7°C over the same span.
December is one of the cooler months of the year in Llanelli and a relatively wet time of year, so plan for around 9.2°C daytime highs and 6.7°C at night.
Not quite — December is the 4th coolest month in Llanelli, averaging 8°C.
For December in Llanelli, pack warm layers and a jacket for chilly mornings, with typical highs of 9.2°C and lows of 6.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 88% — quite humid.
Average wind speed in December is 6.3 m/s. The windiest December on record averaged 8 m/s (2015).
The wettest December on record was 2020 with 278 mm. On average, December sees 139 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Llanelli behaves each December, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for December specifically, along with year-by-year records and how the month has changed over the decades.
