December is one of the cooler months of the year in Williamsport, with average highs near 1.1°C and lows around -6°C (mean -2.4°C). It is one of the drier months, averaging 76 mm of rainfall and 88% relative humidity across the period.
December is one of the cooler months of the year in Williamsport. Across 45 years of records, the warmest December in Williamsport was 2015 — when the month averaged 4.4°C — while the coldest was 1989 at -8.7°C. Typical December days reach 1.1°C with nights near -6°C. The long-term trend is warming, about 0.4°C per decade.
December is one of the drier months in Williamsport, averaging 76 mm of rainfall. The wettest December on record was 1983 with 156 mm, while the driest was 1989 at 27 mm.
Relative humidity in Williamsport during December averages 88%. The most humid December was 2005 at 93%, and the least humid was 1998 at 78%.
December receives about 1.4 kWh/m²/day of solar energy in Williamsport. The sunniest December was 1995 at 1.7 kWh/m²/day, and the cloudiest were 2007, 2013 and 2014 at 1.1.
Average wind speed in Williamsport during December is 0.3 m/s. The windiest Decembers were 2020, 2024 and 2025, among others at 0.3 m/s, while the calmest were 2021, 2022 and 2023, among others at 0.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | -3.6°C | -1.9°C | -3.1°C | -1.6°C | -1.8°C | +1.8°C |
| Avg High | -0.1°C | 1.7°C | 0.5°C | 1.6°C | 1.9°C | +2°C |
| Avg Low | -7.1°C | -5.6°C | -6.8°C | -4.8°C | -5.6°C | +1.5°C |
| Avg Rain | 59 mm | 73 mm | 82 mm | 80 mm | 90 mm | +31 mm |
December temperatures in Williamsport have risen by about 1.4°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -26.2°C (1983) to a record high of 19.1°C (1998).
Rainfall in December is one of the drier months, averaging 76 mm, with a wettest year of 156 mm.
A quieter season to visit Williamsport
If your dates are flexible, the more temperate months of July and August tend to be the most comfortable for visiting Williamsport. That said, December — with days averaging 1.1°C and nights around -6°C (mean -2.4°C) and moderate rainfall (76 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 | -0.9°C | -4.8°C | -8.7°C | 8.3°C | -14.6°C | 66 mm | 86% | 0.3 m/s | — |
| 2024 | 0.9°C | -2.6°C | -6.2°C | 11.2°C | -15.2°C | 74 mm | 89% | 0.3 m/s | 1.4 |
| 2023 | 4.7°C | 1.1°C | -2.4°C | 8.6°C | -8.1°C | 142 mm | 92% | 0.2 m/s | 1.3 |
| 2022 | 0.5°C | -3.4°C | -7.4°C | 8.5°C | -20.7°C | 95 mm | 92% | 0.2 m/s | 1.4 |
| 2021 | 4.6°C | 0.9°C | -2.8°C | 13.5°C | -8.6°C | 44 mm | 89% | 0.2 m/s | 1.5 |
| 2020 | 1.6°C | -2.2°C | -5.9°C | 12.0°C | -16.4°C | 117 mm | 88% | 0.3 m/s | 1.3 |
| 2019 | 1.2°C | -2.1°C | -5.4°C | 8.0°C | -13.5°C | 78 mm | 91% | 0.3 m/s | 1.4 |
| 2018 | 1.7°C | -1.3°C | -4.3°C | 12.3°C | -9.6°C | 109 mm | 93% | 0.2 m/s | 1.3 |
| 2017 | -1.0°C | -3.9°C | -6.8°C | 8.3°C | -17.1°C | 31 mm | 81% | 0.3 m/s | 1.4 |
| 2016 | 0.6°C | -2.7°C | -6.1°C | 8.2°C | -13.1°C | 63 mm | 87% | 0.3 m/s | 1.3 |
| 2015 🔥 | 8.2°C | 4.4°C | 0.7°C | 16.8°C | -4.9°C | 91 mm | 90% | 0.3 m/s | 1.2 |
| 2014 | 1.4°C | -1.8°C | -5.0°C | 9.2°C | -11.5°C | 70 mm | 89% | 0.2 m/s | 1.1 |
| 2013 | 0.1°C | -3.1°C | -6.4°C | 15.4°C | -15.3°C | 82 mm | 90% | 0.3 m/s | 1.1 |
| 2012 | 2.8°C | -0.3°C | -3.5°C | 17.2°C | -13.0°C | 124 mm | 93% | 0.3 m/s | 1.2 |
| 2011 | 3.2°C | -0.2°C | -3.6°C | 11.5°C | -11.3°C | 84 mm | 92% | 0.3 m/s | 1.5 |
| 2010 | -1.8°C | -4.9°C | -8.0°C | 13.1°C | -12.7°C | 65 mm | 86% | 0.3 m/s | 1.5 |
| 2009 | -0.4°C | -3.6°C | -6.9°C | 9.5°C | -13.8°C | 81 mm | 88% | 0.3 m/s | 1.4 |
| 2008 | -0.6°C | -4.4°C | -8.2°C | 8.4°C | -19.2°C | 111 mm | 92% | 0.3 m/s | 1.3 |
| 2007 | 0.1°C | -3.2°C | -6.5°C | 8.8°C | -16.6°C | 114 mm | 93% | 0.3 m/s | 1.1 |
| 2006 | 5.0°C | 0.9°C | -3.2°C | 18.9°C | -11.6°C | 56 mm | 88% | 0.2 m/s | 1.5 |
| 2005 | -2.3°C | -5.6°C | -8.8°C | 2.7°C | -16.5°C | 64 mm | 93% | 0.3 m/s | 1.3 |
| 2004 | 1.0°C | -2.8°C | -6.7°C | 10.7°C | -18.6°C | 90 mm | 89% | 0.3 m/s | 1.3 |
| 2003 | 0.8°C | -2.7°C | -6.1°C | 6.9°C | -11.3°C | 101 mm | 89% | 0.3 m/s | 1.4 |
| 2002 | -0.8°C | -4.4°C | -8.1°C | 4.9°C | -18.7°C | 87 mm | 91% | 0.3 m/s | 1.4 |
| 2001 | 4.5°C | 0.8°C | -2.9°C | 18.8°C | -10.8°C | 46 mm | 84% | 0.3 m/s | 1.6 |
| 2000 | -2.4°C | -6.4°C | -10.3°C | 9.2°C | -18.5°C | 69 mm | 83% | 0.3 m/s | 1.6 |
| 1999 | 2.5°C | -1.4°C | -5.3°C | 14.5°C | -12.9°C | 51 mm | 85% | 0.3 m/s | 1.4 |
| 1998 | 5.9°C | 1.3°C | -3.3°C | 19.1°C | -12.1°C | 29 mm | 78% | 0.2 m/s | 1.5 |
| 1997 | 1.2°C | -2.3°C | -5.8°C | 6.7°C | -13.5°C | 55 mm | 90% | 0.3 m/s | 1.4 |
| 1996 | 1.6°C | -1.1°C | -3.9°C | 10.7°C | -13.2°C | 135 mm | 93% | 0.3 m/s | 1.2 |
| 1995 | -2.6°C | -5.7°C | -8.9°C | 5.8°C | -15.1°C | 41 mm | 89% | 0.3 m/s | 1.7 |
| 1994 | 3.1°C | -0.9°C | -4.9°C | 12.4°C | -14.8°C | 65 mm | 89% | 0.3 m/s | 1.4 |
| 1993 | -0.2°C | -3.9°C | -7.5°C | 6.4°C | -18.5°C | 68 mm | 90% | 0.3 m/s | 1.2 |
| 1992 | 0.7°C | -2.8°C | -6.2°C | 10.6°C | -14.9°C | 74 mm | 89% | 0.3 m/s | 1.3 |
| 1991 | 2.1°C | -1.8°C | -5.8°C | 10.6°C | -14.4°C | 76 mm | 86% | 0.3 m/s | 1.4 |
| 1990 | 2.9°C | -0.9°C | -4.8°C | 11.9°C | -12.6°C | 137 mm | 88% | 0.3 m/s | 1.2 |
| 1989 ❄️ | -4.9°C | -8.7°C | -12.4°C | 1.2°C | -17.2°C | 27 mm | 85% | 0.3 m/s | 1.5 |
| 1988 | 0.1°C | -3.6°C | -7.2°C | 7.7°C | -15.5°C | 27 mm | 81% | 0.3 m/s | 1.4 |
| 1987 | 1.5°C | -1.9°C | -5.2°C | 7.1°C | -14.4°C | 43 mm | 88% | 0.3 m/s | 1.2 |
| 1986 | 1.4°C | -2.2°C | -5.8°C | 5.7°C | -13.0°C | 66 mm | 89% | 0.3 m/s | 1.4 |
| 1985 | -1.6°C | -5.1°C | -8.7°C | 6.2°C | -16.6°C | 45 mm | 88% | 0.3 m/s | 1.2 |
| 1984 | 2.8°C | -0.6°C | -4.0°C | 15.7°C | -10.6°C | 68 mm | 91% | 0.3 m/s | 1.3 |
| 1983 🌧️ | -2.9°C | -6.1°C | -9.3°C | 5.7°C | -26.2°C | 156 mm | 90% | 0.3 m/s | — |
| 1982 | 4.0°C | 0.2°C | -3.6°C | 17.5°C | -13.0°C | 46 mm | 85% | 0.2 m/s | — |
| 1981 | -1.3°C | -4.6°C | -7.9°C | 4.2°C | -15.4°C | 53 mm | 91% | 0.3 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 1.1°C with lows near -6°C (mean -2.4°C), based on 45 years of NASA POWER data.
December averages 76 mm of rainfall in Williamsport, one of the drier months. The wettest on record was 156 mm in 1983.
The hottest December reached 19.1°C in 1998. The coldest dipped to -26.2°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.4°C. Daytime highs moved from 0.2°C to 2°C and overnight lows from -6.7°C to -5.5°C over the same span.
December is one of the cooler months of the year in Williamsport and one of the drier months, so plan for around 1.1°C daytime highs and -6°C at night.
Not quite — December is the 3rd coolest month in Williamsport, averaging -2.4°C.
For December in Williamsport, pack warm layers and a jacket for chilly mornings, with typical highs of 1.1°C and lows of -6°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 88% — quite humid.
Average wind speed in December is 0.3 m/s. The windiest December on record averaged 0.3 m/s (1981).
The wettest December on record was 1983 with 156 mm. On average, December sees 76 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 Williamsport 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.
