December is one of the cooler months of the year in Cornwall, with average highs near -1.5°C and lows around -9.4°C (mean -5.4°C). It is about average for rainfall, averaging 74 mm of rainfall and 90% relative humidity across the period.
December is one of the cooler months of the year in Cornwall. Across 45 years of records, the warmest December in Cornwall was 2015 — when the month averaged 1.6°C — while the coldest was 1989 at -16.3°C. Typical December days reach -1.5°C with nights near -9.4°C. The long-term trend is warming, about 0.6°C per decade.
December is about average for rainfall in Cornwall, averaging 74 mm of rainfall. The wettest December on record was 1983 with 144 mm, while the driest was 2002 at 29 mm.
Relative humidity in Cornwall during December averages 90%. The most humid December was 1995 at 99%, and the least humid was 2021 at 81%.
December receives about 1 kWh/m²/day of solar energy in Cornwall. The sunniest December was 1989 at 1.4 kWh/m²/day, and the cloudiest were 2015, 2020 and 2023, among others at 0.9.
Average wind speed in Cornwall during December is 0.8 m/s. The windiest Decembers were 2016, 2022 and 2025, among others at 0.9 m/s, while the calmest were 2013, 2018 and 2023, among others at 0.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | -7.2°C | -5.1°C | -5.9°C | -5.0°C | -3.6°C | +3.6°C |
| Avg High | -3.1°C | -1.1°C | -2.0°C | -1.1°C | 0.1°C | +3.2°C |
| Avg Low | -11.4°C | -9.2°C | -9.9°C | -8.8°C | -7.2°C | +4.2°C |
| Avg Rain | 74 mm | 73 mm | 83 mm | 69 mm | 67 mm | -8 mm |
December temperatures in Cornwall have risen by about 2.5°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -40.3°C (1993) to a record high of 18.3°C (2015).
Rainfall in December is about average for rainfall, averaging 74 mm, with a wettest year of 144 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.6°C per decade while lows rose 0.8°C per decade, narrowing the gap between day and night.
A quieter season to visit Cornwall
If your dates are flexible, the more temperate months of July and August tend to be the most comfortable for visiting Cornwall. That said, December — with days averaging -1.5°C and nights around -9.4°C (mean -5.4°C) and moderate rainfall (74 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 | -3.1°C | -7.5°C | -11.8°C | 9.5°C | -21.6°C | 61 mm | 85% | 0.9 m/s | — |
| 2024 | -0.7°C | -4.0°C | -7.2°C | 8.6°C | -19.8°C | 73 mm | 87% | 0.8 m/s | 1 |
| 2023 | 1.4°C | -2.0°C | -5.4°C | 7.7°C | -16.9°C | 97 mm | 91% | 0.7 m/s | 0.9 |
| 2022 | 0.9°C | -2.8°C | -6.4°C | 9.2°C | -12.8°C | 73 mm | 87% | 0.9 m/s | 1 |
| 2021 | 1.4°C | -2.5°C | -6.3°C | 14.8°C | -13.5°C | 42 mm | 81% | 0.8 m/s | 1 |
| 2020 | 0.8°C | -2.7°C | -6.3°C | 10.0°C | -16.0°C | 54 mm | 82% | 0.8 m/s | 0.9 |
| 2019 | -0.7°C | -4.7°C | -8.6°C | 5.9°C | -20.9°C | 45 mm | 88% | 0.8 m/s | 1.1 |
| 2018 | -0.9°C | -5.5°C | -10.0°C | 7.7°C | -18.2°C | 63 mm | 89% | 0.7 m/s | 1.1 |
| 2017 | -5.0°C | -8.3°C | -11.5°C | 10.1°C | -29.8°C | 47 mm | 87% | 0.8 m/s | 1.1 |
| 2016 | -0.3°C | -4.3°C | -8.3°C | 7.8°C | -22.0°C | 76 mm | 87% | 0.9 m/s | 1 |
| 2015 🔥 | 5.2°C | 1.6°C | -2.0°C | 18.3°C | -11.2°C | 80 mm | 88% | 0.8 m/s | 0.9 |
| 2014 | -0.7°C | -4.3°C | -7.9°C | 8.0°C | -17.3°C | 50 mm | 86% | 0.8 m/s | 1 |
| 2013 | -4.8°C | -8.9°C | -13.0°C | 5.4°C | -27.3°C | 69 mm | 92% | 0.7 m/s | 1 |
| 2012 | -0.9°C | -5.0°C | -9.1°C | 16.9°C | -22.1°C | 118 mm | 92% | 0.8 m/s | 1 |
| 2011 | 1.0°C | -3.2°C | -7.3°C | 9.3°C | -21.7°C | 78 mm | 87% | 0.8 m/s | 1 |
| 2010 | -3.6°C | -7.0°C | -10.5°C | 12.0°C | -22.2°C | 62 mm | 92% | 0.7 m/s | 1 |
| 2009 | -3.3°C | -7.0°C | -10.7°C | 9.0°C | -26.1°C | 84 mm | 93% | 0.8 m/s | 1.2 |
| 2008 | -2.4°C | -7.0°C | -11.6°C | 11.7°C | -26.1°C | 105 mm | 88% | 0.9 m/s | 1 |
| 2007 | -4.0°C | -7.8°C | -11.7°C | 2.4°C | -24.6°C | 104 mm | 96% | 0.8 m/s | 1 |
| 2006 | 2.1°C | -1.4°C | -4.9°C | 10.7°C | -15.3°C | 93 mm | 89% | 0.9 m/s | 1.1 |
| 2005 | -2.9°C | -6.6°C | -10.3°C | 3.4°C | -25.2°C | 58 mm | 92% | 0.8 m/s | 1.1 |
| 2004 | -2.8°C | -7.5°C | -12.3°C | 8.9°C | -29.2°C | 101 mm | 92% | 0.9 m/s | 1 |
| 2003 | -1.9°C | -5.7°C | -9.5°C | 5.7°C | -20.1°C | 111 mm | 92% | 0.8 m/s | 1.1 |
| 2002 | -1.3°C | -5.0°C | -8.8°C | 5.6°C | -19.4°C | 29 mm | 89% | 0.8 m/s | 1.1 |
| 2001 | 2.6°C | -0.9°C | -4.5°C | 13.6°C | -13.7°C | 65 mm | 91% | 0.8 m/s | 1.2 |
| 2000 | -6.2°C | -10.5°C | -14.9°C | 5.8°C | -24.3°C | 79 mm | 92% | 0.8 m/s | 1.1 |
| 1999 | 0.3°C | -3.7°C | -7.6°C | 15.2°C | -19.3°C | 69 mm | 86% | 0.9 m/s | 0.9 |
| 1998 | 3.3°C | -1.3°C | -5.9°C | 16.3°C | -21.4°C | 56 mm | 86% | 0.9 m/s | 1.1 |
| 1997 | -2.8°C | -6.9°C | -11.1°C | 3.3°C | -27.5°C | 51 mm | 95% | 0.7 m/s | 1.2 |
| 1996 | 0.5°C | -2.4°C | -5.3°C | 7.1°C | -23.3°C | 112 mm | 92% | 0.7 m/s | 0.9 |
| 1995 | -6.5°C | -10.7°C | -14.9°C | 0.3°C | -27.1°C | 59 mm | 99% | 0.7 m/s | 1.3 |
| 1994 | 0.2°C | -3.8°C | -7.8°C | 7.8°C | -19.7°C | 50 mm | 89% | 0.7 m/s | 1 |
| 1993 | -2.5°C | -7.3°C | -12.0°C | 5.3°C | -40.3°C | 73 mm | 93% | 0.8 m/s | 1 |
| 1992 | -0.6°C | -4.3°C | -8.0°C | 5.9°C | -17.5°C | 48 mm | 87% | 0.9 m/s | 0.9 |
| 1991 | -2.3°C | -6.4°C | -10.6°C | 10.0°C | -24.8°C | 71 mm | 88% | 0.8 m/s | 1 |
| 1990 | -0.3°C | -4.6°C | -8.9°C | 5.8°C | -19.7°C | 142 mm | 90% | 0.8 m/s | 1.1 |
| 1989 ❄️ | -11.3°C | -16.3°C | -21.3°C | 0.3°C | -32.8°C | 31 mm | 93% | 0.8 m/s | 1.4 |
| 1988 | -2.4°C | -6.6°C | -10.8°C | 6.7°C | -21.1°C | 47 mm | 83% | 0.8 m/s | 1 |
| 1987 | -0.5°C | -3.9°C | -7.3°C | 7.2°C | -19.4°C | 59 mm | 92% | 0.8 m/s | 1 |
| 1986 | -2.3°C | -6.7°C | -11.1°C | 1.2°C | -21.1°C | 89 mm | 96% | 0.8 m/s | 1 |
| 1985 | -4.0°C | -8.3°C | -12.6°C | 6.3°C | -29.9°C | 60 mm | 93% | 0.8 m/s | 1 |
| 1984 | -0.3°C | -3.9°C | -7.5°C | 8.2°C | -20.4°C | 106 mm | 87% | 0.9 m/s | 0.9 |
| 1983 🌧️ | -5.9°C | -10.7°C | -15.5°C | 0.4°C | -39.5°C | 144 mm | 97% | 0.9 m/s | — |
| 1982 | 1.0°C | -3.2°C | -7.4°C | 14.1°C | -22.3°C | 87 mm | 87% | 0.9 m/s | — |
| 1981 | -2.4°C | -5.6°C | -8.7°C | 6.2°C | -23.1°C | 47 mm | 93% | 0.7 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around -1.5°C with lows near -9.4°C (mean -5.4°C), based on 45 years of NASA POWER data.
December averages 74 mm of rainfall in Cornwall, about average for rainfall. The wettest on record was 144 mm in 1983.
The hottest December reached 18.3°C in 2015. The coldest dipped to -40.3°C in 1993.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 2.5°C. Daytime highs moved from -2.3°C to 0°C and overnight lows from -10.3°C to -7.4°C over the same span.
December is one of the cooler months of the year in Cornwall and about average for rainfall, so plan for around -1.5°C daytime highs and -9.4°C at night.
Not quite — December is the 3rd coolest month in Cornwall, averaging -5.4°C.
For December in Cornwall, pack warm layers and a jacket for chilly mornings, with typical highs of -1.5°C and lows of -9.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 90% — quite humid.
Average wind speed in December is 0.8 m/s. The windiest December on record averaged 0.9 m/s (1982).
The wettest December on record was 1983 with 144 mm. On average, December sees 74 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 Cornwall 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.
