December is one of the cooler months of the year in Portsmouth, with average highs near 8°C and lows around 3.3°C (mean 5.7°C). It is a relatively wet time of year, averaging 88 mm of rainfall and 94% relative humidity across the period.
December is one of the cooler months of the year in Portsmouth. Across 45 years of records, the warmest December in Portsmouth was 2015 — when the month averaged 10.2°C — while the coldest was 2010 at 0.6°C. Typical December days reach 8°C with nights near 3.3°C. The long-term trend is warming, about 0.4°C per decade.
December is a relatively wet time of year in Portsmouth, averaging 88 mm of rainfall. The wettest December on record was 2012 with 150 mm, while the driest was 1988 at 22 mm.
Relative humidity in Portsmouth during December averages 94%. The most humid December was 2010 at 96%, and the least humid was 2015 at 91%.
December receives about 0.7 kWh/m²/day of solar energy in Portsmouth. The sunniest Decembers were 2001, 2008 and 2016 at 0.8 kWh/m²/day, and the cloudiest were 1998 and 2002 at 0.5.
Average wind speed in Portsmouth during December is 4 m/s. The windiest December was 2015 at 5.5 m/s, while the calmest was 2016 at 2.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 5.6°C | 5.0°C | 5.4°C | 6.1°C | 6.6°C | +1°C |
| Avg High | 7.9°C | 7.4°C | 7.6°C | 8.5°C | 8.9°C | +1°C |
| Avg Low | 3.2°C | 2.7°C | 3.1°C | 3.6°C | 4.4°C | +1.2°C |
| Avg Rain | 86 mm | 87 mm | 80 mm | 91 mm | 99 mm | +13 mm |
December temperatures in Portsmouth have risen by about 1.8°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -6.2°C (1981) to a record high of 14.3°C (2024).
Rainfall in December is a relatively wet time of year, averaging 88 mm, with a wettest year of 150 mm.
A quieter season to visit Portsmouth
If your dates are flexible, the more temperate months of July and August tend to be the most comfortable for visiting Portsmouth. That said, December — with days averaging 8°C and nights around 3.3°C (mean 5.7°C) and higher rainfall (88 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 | 9.5°C | 7.2°C | 4.9°C | 13.4°C | -1.1°C | 119 mm | 94% | 4.3 m/s | — |
| 2024 | 9.3°C | 7.2°C | 5.1°C | 14.3°C | 1.9°C | 50 mm | 94% | 4.2 m/s | 0.6 |
| 2023 | 9.8°C | 7.7°C | 5.6°C | 13.2°C | -2.3°C | 125 mm | 94% | 4.8 m/s | 0.6 |
| 2022 | 7.1°C | 4.9°C | 2.6°C | 12.5°C | -4.1°C | 96 mm | 95% | 3.8 m/s | 0.7 |
| 2021 | 9.6°C | 7.2°C | 4.8°C | 13.7°C | -1.1°C | 78 mm | 94% | 3.8 m/s | 0.6 |
| 2020 | 7.8°C | 5.5°C | 3.3°C | 12.7°C | -2.1°C | 126 mm | 95% | 3.9 m/s | 0.7 |
| 2019 | 8.8°C | 6.4°C | 3.9°C | 12.2°C | -1.6°C | 127 mm | 94% | 4 m/s | 0.7 |
| 2018 | 9.8°C | 7.5°C | 5.3°C | 13.4°C | -1.9°C | 112 mm | 94% | 3.9 m/s | 0.6 |
| 2017 | 7.9°C | 5.3°C | 2.7°C | 12.5°C | -3.5°C | 107 mm | 95% | 4.1 m/s | 0.7 |
| 2016 | 9.3°C | 6.9°C | 4.4°C | 12.6°C | -1.8°C | 24 mm | 96% | 2.8 m/s | 0.8 |
| 2015 🔥 | 12.1°C | 10.2°C | 8.4°C | 13.8°C | 3.9°C | 88 mm | 91% | 5.5 m/s | 0.6 |
| 2014 | 8.3°C | 5.4°C | 2.6°C | 12.1°C | -2.0°C | 52 mm | 94% | 4.2 m/s | 0.7 |
| 2013 | 9.3°C | 6.4°C | 3.5°C | 12.2°C | -0.7°C | 118 mm | 94% | 4.3 m/s | 0.7 |
| 2012 🌧️ | 7.8°C | 5.4°C | 3.0°C | 12.4°C | -3.7°C | 150 mm | 95% | 4.3 m/s | 0.7 |
| 2011 | 9.0°C | 6.5°C | 3.9°C | 12.2°C | -1.2°C | 93 mm | 93% | 4.6 m/s | 0.7 |
| 2010 ❄️ | 2.6°C | 0.6°C | -1.4°C | 6.7°C | -5.1°C | 40 mm | 96% | 3.1 m/s | 0.6 |
| 2009 | 6.4°C | 4.1°C | 1.8°C | 12.1°C | -4.0°C | 97 mm | 94% | 3.7 m/s | 0.7 |
| 2008 | 6.4°C | 4.1°C | 1.8°C | 12.0°C | -1.9°C | 45 mm | 95% | 3.4 m/s | 0.8 |
| 2007 | 8.4°C | 5.8°C | 3.2°C | 13.5°C | -1.5°C | 58 mm | 93% | 4.3 m/s | 0.7 |
| 2006 | 9.3°C | 7.2°C | 5.2°C | 13.1°C | 0.5°C | 93 mm | 93% | 4.5 m/s | 0.6 |
| 2005 | 7.3°C | 4.9°C | 2.5°C | 11.1°C | -3.5°C | 69 mm | 95% | 3.5 m/s | 0.7 |
| 2004 | 8.0°C | 5.6°C | 3.2°C | 11.5°C | -1.8°C | 61 mm | 95% | 3.2 m/s | 0.6 |
| 2003 | 8.0°C | 5.6°C | 3.3°C | 12.4°C | -1.4°C | 88 mm | 94% | 3.7 m/s | 0.6 |
| 2002 | 8.1°C | 6.3°C | 4.5°C | 12.3°C | -1.7°C | 112 mm | 95% | 4 m/s | 0.5 |
| 2001 | 6.3°C | 3.6°C | 0.9°C | 13.2°C | -2.7°C | 31 mm | 94% | 3.7 m/s | 0.8 |
| 2000 | 8.0°C | 6.3°C | 4.6°C | 12.6°C | -2.0°C | 142 mm | 95% | 4.7 m/s | 0.6 |
| 1999 | 7.8°C | 5.3°C | 2.9°C | 12.2°C | -5.5°C | 140 mm | 94% | 4.8 m/s | 0.6 |
| 1998 | 8.6°C | 6.1°C | 3.6°C | 12.9°C | -3.6°C | 95 mm | 95% | 4 m/s | 0.5 |
| 1997 | 8.5°C | 6.3°C | 4.1°C | 13.4°C | -1.7°C | 89 mm | 95% | 4.2 m/s | 0.6 |
| 1996 | 5.0°C | 3.0°C | 0.9°C | 11.7°C | -4.6°C | 30 mm | 93% | 3.7 m/s | 0.6 |
| 1995 | 5.7°C | 3.3°C | 1.0°C | 13.1°C | -4.7°C | 101 mm | 95% | 3.4 m/s | 0.6 |
| 1994 | 9.4°C | 7.0°C | 4.6°C | 13.2°C | -1.9°C | 96 mm | 94% | 4.6 m/s | 0.7 |
| 1993 | 8.2°C | 5.7°C | 3.3°C | 12.8°C | -2.5°C | 136 mm | 93% | 5.2 m/s | 0.7 |
| 1992 | 6.7°C | 4.3°C | 1.8°C | 12.9°C | -1.6°C | 83 mm | 96% | 3.7 m/s | 0.6 |
| 1991 | 7.3°C | 5.0°C | 2.8°C | 12.6°C | -3.0°C | 29 mm | 92% | 3.4 m/s | 0.7 |
| 1990 | 7.0°C | 4.3°C | 1.5°C | 11.4°C | -2.9°C | 67 mm | 92% | 4.2 m/s | 0.6 |
| 1989 | 8.3°C | 6.2°C | 4.0°C | 12.8°C | -1.6°C | 144 mm | 93% | 4.3 m/s | 0.7 |
| 1988 | 9.2°C | 6.9°C | 4.6°C | 12.4°C | 0.6°C | 22 mm | 94% | 3.4 m/s | 0.6 |
| 1987 | 7.9°C | 6.0°C | 4.1°C | 13.0°C | -2.4°C | 44 mm | 95% | 4.2 m/s | 0.6 |
| 1986 | 8.6°C | 6.0°C | 3.5°C | 13.3°C | -2.0°C | 96 mm | 94% | 4.9 m/s | 0.7 |
| 1985 | 8.8°C | 6.8°C | 4.8°C | 12.5°C | -4.9°C | 118 mm | 94% | 4 m/s | 0.6 |
| 1984 | 8.2°C | 5.8°C | 3.3°C | 11.4°C | -0.8°C | 99 mm | 95% | 3 m/s | 0.7 |
| 1983 | 8.5°C | 6.0°C | 3.5°C | 11.7°C | -3.6°C | 75 mm | 92% | 4.1 m/s | — |
| 1982 | 7.3°C | 4.7°C | 2.1°C | 11.8°C | -3.4°C | 87 mm | 94% | 3.9 m/s | — |
| 1981 | 4.4°C | 1.8°C | -0.7°C | 10.0°C | -6.2°C | 91 mm | 95% | 3.6 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 8°C with lows near 3.3°C (mean 5.7°C), based on 45 years of NASA POWER data.
December averages 88 mm of rainfall in Portsmouth, a relatively wet time of year. The wettest on record was 150 mm in 2012.
The hottest December reached 14.3°C in 2024. The coldest dipped to -6.2°C in 1981.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.8°C. Daytime highs moved from 7.4°C to 9.1°C and overnight lows from 2.6°C to 4.6°C over the same span.
December is one of the cooler months of the year in Portsmouth and a relatively wet time of year, so plan for around 8°C daytime highs and 3.3°C at night.
Not quite — December is the 3rd coolest month in Portsmouth, averaging 5.7°C.
For December in Portsmouth, pack warm layers and a jacket for chilly mornings, with typical highs of 8°C and lows of 3.3°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 94% — quite humid.
Average wind speed in December is 4 m/s. The windiest December on record averaged 5.5 m/s (2015).
The wettest December on record was 2012 with 150 mm. On average, December sees 88 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 Portsmouth 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.
