December is one of the cooler months of the year in Swansea, with average highs near 8.4°C and lows around 5.2°C (mean 6.8°C). It is a relatively wet time of year, averaging 124 mm of rainfall and 91% relative humidity across the period.
December is one of the cooler months of the year in Swansea. Across 45 years of records, the warmest December in Swansea was 2015 — when the month averaged 10.4°C — while the coldest was 2010 at 2.4°C. Typical December days reach 8.4°C with nights near 5.2°C. The long-term trend is warming, about 0.4°C per decade.
December is a relatively wet time of year in Swansea, averaging 124 mm of rainfall. The wettest December on record was 2020 with 218 mm, while the driest was 2010 at 36 mm.
Relative humidity in Swansea during December averages 91%. The most humid December was 1987 at 94%, and the least humid was 2011 at 87%.
December receives about 0.6 kWh/m²/day of solar energy in Swansea. The sunniest December was 2001 at 0.8 kWh/m²/day, and the cloudiest were 2015, 2018 and 2021, among others at 0.5.
Average wind speed in Swansea during December is 5.3 m/s. The windiest December was 2015 at 6.9 m/s, while the calmest was 2016 at 3.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 6.7°C | 6.1°C | 6.6°C | 7.3°C | 7.6°C | +0.9°C |
| Avg High | 8.3°C | 7.8°C | 8.2°C | 8.9°C | 9.0°C | +0.7°C |
| Avg Low | 5.1°C | 4.5°C | 5.1°C | 5.8°C | 6.1°C | +1°C |
| Avg Rain | 113 mm | 118 mm | 109 mm | 135 mm | 160 mm | +48 mm |
December temperatures in Swansea have risen by about 1.3°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -3°C (1996) to a record high of 14.1°C (1985).
Rainfall in December is a relatively wet time of year, averaging 124 mm, with a wettest year of 218 mm.
A quieter season to visit Swansea
If your dates are flexible, the more temperate months of July and August tend to be the most comfortable for visiting Swansea. That said, December — with days averaging 8.4°C and nights around 5.2°C (mean 6.8°C) and higher rainfall (124 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 | 9.3°C | 7.8°C | 6.4°C | 13.6°C | 1.6°C | 182 mm | 92% | 5.5 m/s | — |
| 2024 | 9.4°C | 8.1°C | 6.7°C | 13.2°C | 4.1°C | 106 mm | 91% | 5.2 m/s | 0.6 |
| 2023 | 9.9°C | 8.6°C | 7.4°C | 12.3°C | 0.2°C | 216 mm | 91% | 5.9 m/s | 0.6 |
| 2022 | 7.5°C | 6.0°C | 4.5°C | 12.8°C | -0.8°C | 110 mm | 92% | 4.6 m/s | 0.7 |
| 2021 | 9.5°C | 8.0°C | 6.5°C | 12.4°C | 2.8°C | 131 mm | 92% | 5.2 m/s | 0.5 |
| 2020 🌧️ | 8.5°C | 7.0°C | 5.4°C | 12.4°C | 1.6°C | 218 mm | 91% | 5.1 m/s | 0.6 |
| 2019 | 9.0°C | 7.5°C | 6.0°C | 12.3°C | 2.0°C | 172 mm | 91% | 5.2 m/s | 0.6 |
| 2018 | 10.0°C | 8.6°C | 7.2°C | 12.6°C | 1.1°C | 188 mm | 92% | 5.3 m/s | 0.5 |
| 2017 | 8.5°C | 6.8°C | 5.1°C | 12.3°C | 1.7°C | 151 mm | 91% | 5.2 m/s | 0.7 |
| 2016 | 9.4°C | 7.8°C | 6.3°C | 12.4°C | 1.9°C | 52 mm | 93% | 3.8 m/s | 0.6 |
| 2015 🔥 | 11.8°C | 10.4°C | 9.0°C | 13.2°C | 5.8°C | 203 mm | 91% | 6.9 m/s | 0.5 |
| 2014 | 8.9°C | 7.2°C | 5.4°C | 11.6°C | 1.5°C | 94 mm | 88% | 5.5 m/s | 0.7 |
| 2013 | 9.8°C | 8.0°C | 6.2°C | 12.3°C | 4.4°C | 100 mm | 88% | 5.7 m/s | 0.6 |
| 2012 | 8.3°C | 6.8°C | 5.2°C | 11.5°C | 0.7°C | 209 mm | 91% | 5.4 m/s | 0.6 |
| 2011 | 9.4°C | 7.9°C | 6.3°C | 12.1°C | 3.3°C | 146 mm | 87% | 6.3 m/s | 0.6 |
| 2010 ❄️ | 3.9°C | 2.4°C | 0.8°C | 8.2°C | -2.2°C | 36 mm | 91% | 4 m/s | 0.6 |
| 2009 | 6.9°C | 5.4°C | 3.8°C | 11.7°C | -0.4°C | 109 mm | 90% | 4.9 m/s | 0.7 |
| 2008 | 7.0°C | 5.4°C | 3.8°C | 10.9°C | -0.1°C | 73 mm | 92% | 4.5 m/s | 0.7 |
| 2007 | 8.7°C | 7.1°C | 5.5°C | 13.2°C | 1.2°C | 118 mm | 91% | 6 m/s | 0.6 |
| 2006 | 9.5°C | 8.1°C | 6.7°C | 12.9°C | 1.7°C | 132 mm | 89% | 6 m/s | 0.6 |
| 2005 | 8.1°C | 6.5°C | 4.9°C | 10.9°C | -0.5°C | 92 mm | 91% | 4.5 m/s | 0.6 |
| 2004 | 9.0°C | 7.5°C | 6.0°C | 11.6°C | 1.7°C | 92 mm | 91% | 4.6 m/s | 0.6 |
| 2003 | 8.5°C | 6.7°C | 5.0°C | 12.0°C | 0.6°C | 126 mm | 92% | 5.1 m/s | 0.6 |
| 2002 | 8.0°C | 6.6°C | 5.2°C | 11.8°C | 0.4°C | 141 mm | 93% | 5.4 m/s | 0.5 |
| 2001 | 7.4°C | 5.5°C | 3.6°C | 12.8°C | -0.3°C | 55 mm | 89% | 5 m/s | 0.8 |
| 2000 | 8.4°C | 7.2°C | 6.0°C | 12.6°C | 0.5°C | 158 mm | 91% | 6 m/s | 0.5 |
| 1999 | 8.5°C | 7.0°C | 5.4°C | 12.0°C | -0.7°C | 205 mm | 88% | 6.5 m/s | 0.6 |
| 1998 | 9.1°C | 7.2°C | 5.4°C | 12.5°C | -0.2°C | 121 mm | 91% | 5 m/s | 0.5 |
| 1997 | 9.0°C | 7.4°C | 5.9°C | 12.8°C | -0.5°C | 121 mm | 91% | 5.5 m/s | 0.5 |
| 1996 | 5.7°C | 4.0°C | 2.3°C | 11.3°C | -3.0°C | 41 mm | 91% | 4.9 m/s | 0.6 |
| 1995 | 5.7°C | 4.0°C | 2.4°C | 12.4°C | -2.2°C | 112 mm | 93% | 4.9 m/s | 0.6 |
| 1994 | 9.9°C | 8.3°C | 6.6°C | 13.0°C | 1.3°C | 158 mm | 90% | 6.2 m/s | 0.6 |
| 1993 | 8.5°C | 6.7°C | 4.9°C | 11.8°C | 0.2°C | 194 mm | 89% | 6.6 m/s | 0.6 |
| 1992 | 7.1°C | 5.4°C | 3.7°C | 12.1°C | -0.6°C | 97 mm | 92% | 4.8 m/s | 0.7 |
| 1991 | 7.6°C | 6.0°C | 4.4°C | 11.4°C | -1.1°C | 39 mm | 91% | 4.8 m/s | 0.7 |
| 1990 | 7.1°C | 5.4°C | 3.7°C | 11.1°C | 0.4°C | 93 mm | 89% | 5.3 m/s | 0.7 |
| 1989 | 7.9°C | 6.3°C | 4.7°C | 12.3°C | 0.7°C | 149 mm | 92% | 5.6 m/s | 0.6 |
| 1988 | 9.6°C | 8.1°C | 6.6°C | 11.7°C | 1.9°C | 39 mm | 92% | 4.5 m/s | 0.5 |
| 1987 | 7.9°C | 6.5°C | 5.1°C | 12.2°C | 0.2°C | 69 mm | 94% | 5.7 m/s | 0.5 |
| 1986 | 9.1°C | 7.3°C | 5.5°C | 13.1°C | 1.2°C | 142 mm | 89% | 6.2 m/s | 0.6 |
| 1985 | 9.2°C | 7.9°C | 6.6°C | 14.1°C | -1.1°C | 134 mm | 90% | 5.2 m/s | 0.5 |
| 1984 | 8.7°C | 7.0°C | 5.2°C | 11.4°C | 2.6°C | 135 mm | 91% | 4.3 m/s | 0.6 |
| 1983 | 9.1°C | 7.4°C | 5.7°C | 12.2°C | 1.7°C | 109 mm | 91% | 5.4 m/s | — |
| 1982 | 7.7°C | 6.0°C | 4.2°C | 12.1°C | 1.3°C | 123 mm | 90% | 5.3 m/s | — |
| 1981 | 5.3°C | 3.6°C | 1.9°C | 10.5°C | -2.2°C | 114 mm | 90% | 4.9 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 8.4°C with lows near 5.2°C (mean 6.8°C), based on 45 years of NASA POWER data.
December averages 124 mm of rainfall in Swansea, a relatively wet time of year. The wettest on record was 218 mm in 2020.
The hottest December reached 14.1°C in 1985. The coldest dipped to -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°C to 9.1°C and overnight lows from 4.7°C to 6.3°C over the same span.
December is one of the cooler months of the year in Swansea and a relatively wet time of year, so plan for around 8.4°C daytime highs and 5.2°C at night.
Not quite — December is the 3rd coolest month in Swansea, averaging 6.8°C.
For December in Swansea, pack warm layers and a jacket for chilly mornings, with typical highs of 8.4°C and lows of 5.2°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 91% — quite humid.
Average wind speed in December is 5.3 m/s. The windiest December on record averaged 6.9 m/s (2015).
The wettest December on record was 2020 with 218 mm. On average, December sees 124 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 Swansea 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.
