December is one of the cooler months of the year in Philadelphia, with average highs near 6.2°C and lows around -2.5°C (mean 1.9°C). It is about average for rainfall, averaging 101 mm of rainfall and 84% relative humidity across the period.
December is one of the cooler months of the year in Philadelphia. Across 45 years of records, the warmest December in Philadelphia was 2015 — when the month averaged 8.7°C — while the coldest was 1989 at -5.3°C. Typical December days reach 6.2°C with nights near -2.5°C. The long-term trend is warming, about 0.5°C per decade.
December is about average for rainfall in Philadelphia, averaging 101 mm of rainfall. The wettest December on record was 2023 with 224 mm, while the driest was 1988 at 23 mm.
Relative humidity in Philadelphia during December averages 84%. The most humid December was 1996 at 91%, and the least humid was 1998 at 75%.
December receives about 1.8 kWh/m²/day of solar energy in Philadelphia. The sunniest Decembers were 2000, 2001 and 2006, among others at 2 kWh/m²/day, and the cloudiest were 1992 and 2014 at 1.4.
Average wind speed in Philadelphia during December is 2 m/s. The windiest Decembers were 2003 and 2010 at 2.5 m/s, while the calmest were 2021 and 2023 at 1.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 0.4°C | 2.2°C | 1.4°C | 2.8°C | 2.5°C | +2.1°C |
| Avg High | 4.7°C | 6.6°C | 5.8°C | 7.0°C | 7.0°C | +2.3°C |
| Avg Low | -3.8°C | -2.3°C | -3.0°C | -1.3°C | -1.9°C | +1.9°C |
| Avg Rain | 77 mm | 102 mm | 111 mm | 107 mm | 111 mm | +34 mm |
December temperatures in Philadelphia have risen by about 1.6°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -18°C (1989) to a record high of 23.7°C (1998).
Rainfall in December is about average for rainfall, averaging 101 mm, with a wettest year of 224 mm.
A quieter season to visit Philadelphia
If your dates are flexible, the more temperate months of June and August tend to be the most comfortable for visiting Philadelphia. That said, December — with days averaging 6.2°C and nights around -2.5°C (mean 1.9°C) and higher rainfall (101 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 | 3.6°C | -0.5°C | -4.5°C | 14.4°C | -10.2°C | 72 mm | 80% | 2.1 m/s | — |
| 2024 | 6.8°C | 2.2°C | -2.3°C | 17.3°C | -12.2°C | 95 mm | 80% | 1.9 m/s | 1.9 |
| 2023 🌧️ | 9.1°C | 4.7°C | 0.3°C | 16.4°C | -5.0°C | 224 mm | 88% | 1.7 m/s | 1.6 |
| 2022 | 6.4°C | 1.7°C | -3.0°C | 15.8°C | -14.4°C | 120 mm | 85% | 2 m/s | 1.9 |
| 2021 | 9.8°C | 5.1°C | 0.5°C | 17.0°C | -6.0°C | 33 mm | 83% | 1.7 m/s | 1.8 |
| 2020 | 6.2°C | 1.8°C | -2.6°C | 16.1°C | -9.6°C | 121 mm | 87% | 2.1 m/s | 1.8 |
| 2019 | 6.4°C | 2.3°C | -1.8°C | 15.1°C | -10.2°C | 123 mm | 87% | 1.8 m/s | 1.6 |
| 2018 | 7.1°C | 3.0°C | -1.1°C | 16.5°C | -6.5°C | 159 mm | 89% | 1.8 m/s | 1.7 |
| 2017 | 4.4°C | 0.3°C | -3.7°C | 16.1°C | -13.6°C | 39 mm | 78% | 1.9 m/s | 1.8 |
| 2016 | 5.9°C | 1.6°C | -2.7°C | 17.3°C | -10.8°C | 77 mm | 81% | 2 m/s | 1.7 |
| 2015 🔥 | 12.9°C | 8.7°C | 4.5°C | 21.5°C | -4.0°C | 126 mm | 87% | 1.8 m/s | 1.5 |
| 2014 | 7.1°C | 3.0°C | -1.1°C | 15.7°C | -4.5°C | 112 mm | 87% | 2 m/s | 1.4 |
| 2013 | 6.0°C | 1.6°C | -2.7°C | 20.3°C | -12.0°C | 125 mm | 88% | 1.8 m/s | 1.6 |
| 2012 | 8.6°C | 4.5°C | 0.3°C | 17.8°C | -4.6°C | 132 mm | 87% | 2 m/s | 1.6 |
| 2011 | 9.0°C | 4.2°C | -0.5°C | 16.1°C | -5.2°C | 110 mm | 87% | 1.8 m/s | 1.9 |
| 2010 | 2.4°C | -1.2°C | -4.7°C | 16.9°C | -8.9°C | 69 mm | 79% | 2.5 m/s | 1.9 |
| 2009 | 4.6°C | 0.5°C | -3.5°C | 18.2°C | -12.8°C | 203 mm | 86% | 2.3 m/s | 1.9 |
| 2008 | 6.1°C | 1.6°C | -2.9°C | 17.8°C | -12.6°C | 150 mm | 86% | 2.2 m/s | 1.7 |
| 2007 | 5.0°C | 1.4°C | -2.2°C | 14.3°C | -7.1°C | 132 mm | 87% | 1.9 m/s | 1.5 |
| 2006 | 9.4°C | 4.6°C | -0.3°C | 20.5°C | -6.7°C | 57 mm | 85% | 1.9 m/s | 2 |
| 2005 | 3.8°C | -0.5°C | -4.7°C | 11.0°C | -14.7°C | 87 mm | 87% | 1.9 m/s | 1.9 |
| 2004 | 6.3°C | 1.8°C | -2.8°C | 15.2°C | -12.2°C | 80 mm | 85% | 2.1 m/s | 1.9 |
| 2003 | 5.6°C | 1.2°C | -3.2°C | 14.6°C | -11.4°C | 147 mm | 87% | 2.5 m/s | 1.9 |
| 2002 | 4.0°C | -0.1°C | -4.2°C | 14.6°C | -11.8°C | 117 mm | 86% | 2.1 m/s | 1.8 |
| 2001 | 10.2°C | 5.1°C | 0.0°C | 22.4°C | -9.5°C | 52 mm | 75% | 1.9 m/s | 2 |
| 2000 | 2.6°C | -1.6°C | -5.9°C | 17.4°C | -13.5°C | 82 mm | 77% | 2.2 m/s | 2 |
| 1999 | 7.3°C | 2.7°C | -1.9°C | 17.9°C | -9.0°C | 74 mm | 82% | 2 m/s | 1.9 |
| 1998 | 9.3°C | 4.4°C | -0.5°C | 23.7°C | -9.0°C | 33 mm | 75% | 1.8 m/s | 1.7 |
| 1997 | 6.4°C | 2.0°C | -2.4°C | 11.8°C | -7.4°C | 92 mm | 84% | 2 m/s | 2 |
| 1996 | 6.8°C | 3.1°C | -0.6°C | 14.2°C | -7.7°C | 205 mm | 91% | 2.1 m/s | 1.6 |
| 1995 | 1.5°C | -2.7°C | -6.9°C | 12.0°C | -14.2°C | 64 mm | 88% | 2.1 m/s | 2 |
| 1994 | 8.2°C | 3.4°C | -1.4°C | 17.0°C | -6.5°C | 64 mm | 84% | 1.9 m/s | 1.7 |
| 1993 | 5.2°C | 0.8°C | -3.5°C | 14.2°C | -11.8°C | 120 mm | 84% | 2.1 m/s | 1.6 |
| 1992 | 5.6°C | 1.6°C | -2.5°C | 16.2°C | -10.9°C | 132 mm | 85% | 2.2 m/s | 1.4 |
| 1991 | 7.0°C | 2.5°C | -2.0°C | 19.6°C | -9.7°C | 106 mm | 82% | 2 m/s | 1.8 |
| 1990 | 8.8°C | 3.8°C | -1.3°C | 18.6°C | -6.9°C | 128 mm | 85% | 2.2 m/s | 1.6 |
| 1989 ❄️ | -0.9°C | -5.3°C | -9.8°C | 8.8°C | -18.0°C | 33 mm | 83% | 2 m/s | 1.9 |
| 1988 | 4.5°C | 0.0°C | -4.4°C | 15.2°C | -14.1°C | 23 mm | 79% | 2 m/s | 1.8 |
| 1987 | 6.3°C | 2.1°C | -2.0°C | 14.8°C | -10.8°C | 54 mm | 84% | 2 m/s | 1.7 |
| 1986 | 6.2°C | 1.9°C | -2.4°C | 14.7°C | -6.7°C | 155 mm | 87% | 1.9 m/s | 1.8 |
| 1985 | 3.5°C | -0.6°C | -4.7°C | 11.1°C | -12.3°C | 28 mm | 81% | 2 m/s | 2 |
| 1984 | 8.6°C | 4.2°C | -0.3°C | 19.0°C | -5.9°C | 62 mm | 87% | 1.8 m/s | 1.7 |
| 1983 | 2.9°C | -1.0°C | -5.0°C | 15.0°C | -17.7°C | 175 mm | 86% | 2.3 m/s | — |
| 1982 | 8.3°C | 3.8°C | -0.7°C | 20.9°C | -9.8°C | 56 mm | 87% | 1.9 m/s | — |
| 1981 | 2.7°C | -1.2°C | -5.1°C | 12.5°C | -17.7°C | 105 mm | 88% | 2 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 6.2°C with lows near -2.5°C (mean 1.9°C), based on 45 years of NASA POWER data.
December averages 101 mm of rainfall in Philadelphia, about average for rainfall. The wettest on record was 224 mm in 2023.
The hottest December reached 23.7°C in 1998. The coldest dipped to -18°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.6°C. Daytime highs moved from 5.2°C to 7.1°C and overnight lows from -3.2°C to -1.8°C over the same span.
December is one of the cooler months of the year in Philadelphia and about average for rainfall, so plan for around 6.2°C daytime highs and -2.5°C at night.
Not quite — December is the 3rd coolest month in Philadelphia, averaging 1.9°C.
For December in Philadelphia, pack warm layers and a jacket for chilly mornings, with typical highs of 6.2°C and lows of -2.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 84% — quite humid.
Average wind speed in December is 2 m/s. The windiest December on record averaged 2.5 m/s (2003).
The wettest December on record was 2023 with 224 mm. On average, December sees 101 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 Philadelphia 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.
