December is one of the cooler months of the year in Gelligaer, with average highs near 7.8°C and lows around 3.8°C (mean 5.8°C). It is a relatively wet time of year, averaging 105 mm of rainfall and 93% relative humidity across the period.
December is one of the cooler months of the year in Gelligaer. Across 45 years of records, the warmest December in Gelligaer was 2015 — when the month averaged 9.9°C — while the coldest was 2010 at 0.9°C. Typical December days reach 7.8°C with nights near 3.8°C. The long-term trend is warming, about 0.4°C per decade.
December is a relatively wet time of year in Gelligaer, averaging 105 mm of rainfall. The wettest December on record was 2012 with 178 mm, while the driest was 2010 at 30 mm.
Relative humidity in Gelligaer during December averages 93%. The most humid December was 2016 at 96%, and the least humid was 2011 at 90%.
December receives about 0.6 kWh/m²/day of solar energy in Gelligaer. 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 Gelligaer during December is 4.4 m/s. The windiest December was 2015 at 6 m/s, while the calmest was 2016 at 3.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 5.7°C | 5.1°C | 5.5°C | 6.3°C | 6.6°C | +0.9°C |
| Avg High | 7.7°C | 7.1°C | 7.4°C | 8.3°C | 8.5°C | +0.8°C |
| Avg Low | 3.6°C | 3.0°C | 3.5°C | 4.3°C | 4.8°C | +1.2°C |
| Avg Rain | 97 mm | 103 mm | 96 mm | 110 mm | 126 mm | +29 mm |
December temperatures in Gelligaer have risen by about 1.5°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -5.7°C (2010) to a record high of 13.7°C (1985).
Rainfall in December is a relatively wet time of year, averaging 105 mm, with a wettest year of 178 mm.
A quieter season to visit Gelligaer
If your dates are flexible, the more temperate months of July and August tend to be the most comfortable for visiting Gelligaer. That said, December — with days averaging 7.8°C and nights around 3.8°C (mean 5.8°C) and higher rainfall (105 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 | 8.8°C | 6.9°C | 5.0°C | 13.3°C | -0.4°C | 147 mm | 94% | 4.6 m/s | — |
| 2024 | 9.0°C | 7.3°C | 5.6°C | 13.4°C | 3.0°C | 85 mm | 93% | 4.5 m/s | 0.6 |
| 2023 | 9.5°C | 7.8°C | 6.1°C | 12.0°C | -2.0°C | 171 mm | 94% | 5.2 m/s | 0.6 |
| 2022 | 6.8°C | 4.8°C | 2.9°C | 12.5°C | -3.4°C | 88 mm | 95% | 3.8 m/s | 0.7 |
| 2021 | 9.1°C | 7.1°C | 5.1°C | 12.8°C | -0.1°C | 99 mm | 94% | 4.2 m/s | 0.5 |
| 2020 | 7.9°C | 5.9°C | 4.0°C | 12.2°C | -0.6°C | 164 mm | 94% | 4.1 m/s | 0.6 |
| 2019 | 8.5°C | 6.5°C | 4.5°C | 12.0°C | -0.2°C | 138 mm | 94% | 4.3 m/s | 0.6 |
| 2018 | 9.5°C | 7.7°C | 5.8°C | 12.6°C | -1.5°C | 150 mm | 94% | 4.4 m/s | 0.5 |
| 2017 | 7.9°C | 5.7°C | 3.6°C | 11.9°C | -1.9°C | 124 mm | 94% | 4.3 m/s | 0.7 |
| 2016 | 8.9°C | 6.9°C | 4.9°C | 12.8°C | -0.4°C | 43 mm | 96% | 3.1 m/s | 0.6 |
| 2015 🔥 | 11.6°C | 9.9°C | 8.1°C | 13.4°C | 4.3°C | 145 mm | 92% | 6 m/s | 0.5 |
| 2014 | 8.2°C | 6.0°C | 3.7°C | 11.1°C | -0.6°C | 77 mm | 92% | 4.6 m/s | 0.7 |
| 2013 | 9.3°C | 6.9°C | 4.6°C | 12.1°C | 1.9°C | 95 mm | 92% | 4.7 m/s | 0.6 |
| 2012 🌧️ | 7.7°C | 5.7°C | 3.8°C | 11.7°C | -1.3°C | 178 mm | 94% | 4.6 m/s | 0.6 |
| 2011 | 8.9°C | 6.9°C | 5.0°C | 11.8°C | 0.8°C | 122 mm | 90% | 5.3 m/s | 0.6 |
| 2010 ❄️ | 2.8°C | 0.9°C | -1.0°C | 7.1°C | -5.7°C | 30 mm | 95% | 3.2 m/s | 0.6 |
| 2009 | 6.0°C | 4.1°C | 2.2°C | 11.5°C | -2.3°C | 99 mm | 94% | 4 m/s | 0.7 |
| 2008 | 6.3°C | 4.2°C | 2.1°C | 11.1°C | -1.7°C | 64 mm | 95% | 3.6 m/s | 0.7 |
| 2007 | 8.0°C | 5.9°C | 3.8°C | 13.2°C | -1.4°C | 96 mm | 93% | 5 m/s | 0.6 |
| 2006 | 8.9°C | 7.2°C | 5.4°C | 12.8°C | -0.3°C | 114 mm | 92% | 5 m/s | 0.6 |
| 2005 | 7.4°C | 5.4°C | 3.3°C | 10.7°C | -2.0°C | 84 mm | 94% | 3.7 m/s | 0.6 |
| 2004 | 8.3°C | 6.3°C | 4.4°C | 11.3°C | -1.2°C | 79 mm | 94% | 3.7 m/s | 0.6 |
| 2003 | 7.8°C | 5.6°C | 3.5°C | 12.0°C | -1.7°C | 110 mm | 94% | 4.2 m/s | 0.6 |
| 2002 | 7.4°C | 5.6°C | 3.9°C | 11.8°C | -1.2°C | 127 mm | 95% | 4.4 m/s | 0.5 |
| 2001 | 6.5°C | 4.2°C | 1.8°C | 12.6°C | -2.3°C | 46 mm | 93% | 4 m/s | 0.8 |
| 2000 | 7.8°C | 6.3°C | 4.8°C | 12.5°C | -1.4°C | 145 mm | 94% | 5 m/s | 0.5 |
| 1999 | 7.9°C | 5.9°C | 4.0°C | 12.0°C | -3.8°C | 169 mm | 92% | 5.4 m/s | 0.6 |
| 1998 | 8.5°C | 6.3°C | 4.1°C | 12.7°C | -2.0°C | 108 mm | 93% | 4.2 m/s | 0.5 |
| 1997 | 8.2°C | 6.3°C | 4.5°C | 12.8°C | -2.0°C | 114 mm | 94% | 4.6 m/s | 0.5 |
| 1996 | 5.0°C | 2.9°C | 0.9°C | 11.0°C | -4.6°C | 37 mm | 93% | 4 m/s | 0.6 |
| 1995 | 4.7°C | 2.6°C | 0.6°C | 12.5°C | -5.5°C | 109 mm | 95% | 3.9 m/s | 0.6 |
| 1994 | 9.3°C | 7.2°C | 5.1°C | 13.1°C | -0.9°C | 131 mm | 93% | 5.2 m/s | 0.6 |
| 1993 | 8.0°C | 5.9°C | 3.8°C | 12.1°C | -1.5°C | 166 mm | 92% | 5.7 m/s | 0.6 |
| 1992 | 6.3°C | 4.2°C | 2.1°C | 12.2°C | -2.4°C | 81 mm | 95% | 3.8 m/s | 0.7 |
| 1991 | 6.9°C | 4.9°C | 2.9°C | 11.5°C | -3.6°C | 33 mm | 92% | 4 m/s | 0.7 |
| 1990 | 6.6°C | 4.4°C | 2.2°C | 11.2°C | -1.8°C | 79 mm | 92% | 4.5 m/s | 0.7 |
| 1989 | 7.2°C | 5.3°C | 3.3°C | 12.2°C | -0.9°C | 141 mm | 94% | 4.6 m/s | 0.6 |
| 1988 | 9.2°C | 7.2°C | 5.3°C | 11.7°C | 0.8°C | 30 mm | 94% | 3.8 m/s | 0.5 |
| 1987 | 7.4°C | 5.6°C | 3.8°C | 12.7°C | -2.4°C | 56 mm | 95% | 4.7 m/s | 0.5 |
| 1986 | 8.5°C | 6.4°C | 4.2°C | 13.3°C | -0.9°C | 115 mm | 92% | 5.3 m/s | 0.6 |
| 1985 | 8.8°C | 7.2°C | 5.5°C | 13.7°C | -3.3°C | 119 mm | 92% | 4.4 m/s | 0.5 |
| 1984 | 8.2°C | 6.0°C | 3.7°C | 11.7°C | 0.4°C | 112 mm | 94% | 3.5 m/s | 0.6 |
| 1983 | 8.6°C | 6.4°C | 4.2°C | 12.5°C | -0.8°C | 88 mm | 93% | 4.6 m/s | — |
| 1982 | 7.2°C | 5.0°C | 2.8°C | 12.0°C | -0.8°C | 100 mm | 93% | 4.4 m/s | — |
| 1981 | 4.3°C | 2.1°C | 0.0°C | 10.5°C | -5.6°C | 106 mm | 93% | 4 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 7.8°C with lows near 3.8°C (mean 5.8°C), based on 45 years of NASA POWER data.
December averages 105 mm of rainfall in Gelligaer, a relatively wet time of year. The wettest on record was 178 mm in 2012.
The hottest December reached 13.7°C in 1985. The coldest dipped to -5.7°C in 2010.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.5°C. Daytime highs moved from 7.4°C to 8.6°C and overnight lows from 3.2°C to 4.9°C over the same span.
December is one of the cooler months of the year in Gelligaer and a relatively wet time of year, so plan for around 7.8°C daytime highs and 3.8°C at night.
Not quite — December is the 3rd coolest month in Gelligaer, averaging 5.8°C.
For December in Gelligaer, pack warm layers and a jacket for chilly mornings, with typical highs of 7.8°C and lows of 3.8°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 93% — quite humid.
Average wind speed in December is 4.4 m/s. The windiest December on record averaged 6 m/s (2015).
The wettest December on record was 2012 with 178 mm. On average, December sees 105 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 Gelligaer 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.
