December is one of the cooler months of the year in Mechanicsburg, with average highs near 4.5°C and lows around -3.5°C (mean 0.5°C). It is about average for rainfall, averaging 87 mm of rainfall and 85% relative humidity across the period.
December is one of the cooler months of the year in Mechanicsburg. Across 45 years of records, the warmest December in Mechanicsburg was 2015 — when the month averaged 7.5°C — while the coldest was 1989 at -5.9°C. Typical December days reach 4.5°C with nights near -3.5°C. The long-term trend is warming, about 0.5°C per decade.
December is about average for rainfall in Mechanicsburg, averaging 87 mm of rainfall. The wettest December on record was 1983 with 184 mm, while the driest was 1998 at 19 mm.
Relative humidity in Mechanicsburg during December averages 85%. The most humid December was 1996 at 92%, and the least humid was 1998 at 72%.
December receives about 1.5 kWh/m²/day of solar energy in Mechanicsburg. The sunniest Decembers were 2000 and 2006 at 1.8 kWh/m²/day, and the cloudiest were 2007, 2014 and 2015 at 1.2.
Average wind speed in Mechanicsburg during December is 1.4 m/s. The windiest December was 2010 at 1.9 m/s, while the calmest were 2021 and 2023 at 1.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | -0.8°C | 1.0°C | -0.2°C | 1.5°C | 1.3°C | +2.1°C |
| Avg High | 3.2°C | 5.0°C | 3.9°C | 5.3°C | 5.6°C | +2.4°C |
| Avg Low | -4.7°C | -3.1°C | -4.2°C | -2.3°C | -3.0°C | +1.7°C |
| Avg Rain | 71 mm | 89 mm | 98 mm | 88 mm | 91 mm | +21 mm |
December temperatures in Mechanicsburg have risen by about 1.9°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -25.6°C (1983) to a record high of 22.8°C (2001).
Rainfall in December is about average for rainfall, averaging 87 mm, with a wettest year of 184 mm.
A quieter season to visit Mechanicsburg
If your dates are flexible, the more temperate months of June and August tend to be the most comfortable for visiting Mechanicsburg. That said, December — with days averaging 4.5°C and nights around -3.5°C (mean 0.5°C) and higher rainfall (87 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 | 2.6°C | -1.4°C | -5.4°C | 9.2°C | -11.8°C | 50 mm | 80% | 1.6 m/s | — |
| 2024 | 5.1°C | 0.9°C | -3.2°C | 15.1°C | -13.0°C | 86 mm | 82% | 1.4 m/s | 1.5 |
| 2023 | 8.0°C | 3.7°C | -0.5°C | 13.1°C | -5.1°C | 151 mm | 88% | 1.2 m/s | 1.3 |
| 2022 | 4.2°C | -0.3°C | -4.8°C | 14.8°C | -17.4°C | 121 mm | 87% | 1.3 m/s | 1.6 |
| 2021 | 9.0°C | 4.4°C | -0.3°C | 16.8°C | -6.0°C | 28 mm | 83% | 1.2 m/s | 1.7 |
| 2020 | 4.4°C | 0.4°C | -3.7°C | 14.3°C | -14.0°C | 112 mm | 88% | 1.5 m/s | 1.4 |
| 2019 | 4.8°C | 1.0°C | -2.7°C | 14.5°C | -11.7°C | 91 mm | 88% | 1.3 m/s | 1.5 |
| 2018 | 5.5°C | 1.8°C | -1.9°C | 16.4°C | -7.7°C | 149 mm | 90% | 1.3 m/s | 1.4 |
| 2017 | 3.2°C | -0.5°C | -4.3°C | 12.7°C | -13.2°C | 31 mm | 78% | 1.4 m/s | 1.6 |
| 2016 | 4.3°C | 0.4°C | -3.6°C | 12.8°C | -12.6°C | 63 mm | 80% | 1.5 m/s | 1.4 |
| 2015 🔥 | 11.5°C | 7.5°C | 3.4°C | 20.3°C | -4.5°C | 105 mm | 88% | 1.3 m/s | 1.2 |
| 2014 | 5.2°C | 1.6°C | -2.0°C | 15.2°C | -4.8°C | 79 mm | 86% | 1.3 m/s | 1.2 |
| 2013 | 3.9°C | -0.2°C | -4.2°C | 19.8°C | -13.6°C | 112 mm | 91% | 1.3 m/s | 1.3 |
| 2012 | 6.9°C | 3.0°C | -0.9°C | 18.6°C | -8.2°C | 96 mm | 89% | 1.5 m/s | 1.3 |
| 2011 | 6.9°C | 2.9°C | -1.2°C | 14.9°C | -5.4°C | 93 mm | 90% | 1.3 m/s | 1.5 |
| 2010 | 1.0°C | -2.5°C | -5.9°C | 15.4°C | -9.0°C | 59 mm | 82% | 1.9 m/s | 1.6 |
| 2009 | 2.5°C | -1.3°C | -5.1°C | 12.8°C | -13.3°C | 146 mm | 88% | 1.5 m/s | 1.5 |
| 2008 | 3.6°C | -0.3°C | -4.1°C | 14.7°C | -13.5°C | 140 mm | 86% | 1.6 m/s | 1.4 |
| 2007 | 3.6°C | 0.0°C | -3.5°C | 14.0°C | -11.8°C | 119 mm | 89% | 1.4 m/s | 1.2 |
| 2006 | 8.2°C | 3.7°C | -0.9°C | 21.6°C | -8.3°C | 59 mm | 84% | 1.4 m/s | 1.8 |
| 2005 | 1.6°C | -2.2°C | -6.1°C | 9.5°C | -14.8°C | 73 mm | 88% | 1.3 m/s | 1.5 |
| 2004 | 5.1°C | 0.9°C | -3.4°C | 14.6°C | -14.2°C | 85 mm | 84% | 1.6 m/s | 1.5 |
| 2003 | 3.5°C | -0.4°C | -4.2°C | 9.4°C | -11.1°C | 113 mm | 87% | 1.6 m/s | 1.5 |
| 2002 | 1.3°C | -2.6°C | -6.5°C | 7.9°C | -13.4°C | 118 mm | 90% | 1.3 m/s | 1.5 |
| 2001 | 8.4°C | 3.9°C | -0.7°C | 22.8°C | -9.5°C | 43 mm | 77% | 1.4 m/s | 1.7 |
| 2000 | 0.8°C | -3.4°C | -7.6°C | 12.4°C | -14.4°C | 82 mm | 78% | 1.5 m/s | 1.8 |
| 1999 | 6.0°C | 1.6°C | -2.9°C | 16.6°C | -10.4°C | 68 mm | 83% | 1.3 m/s | 1.5 |
| 1998 | 8.6°C | 3.9°C | -0.8°C | 22.6°C | -10.6°C | 19 mm | 72% | 1.3 m/s | 1.6 |
| 1997 | 4.8°C | 1.0°C | -2.9°C | 11.7°C | -9.7°C | 53 mm | 87% | 1.4 m/s | 1.6 |
| 1996 | 4.7°C | 1.2°C | -2.3°C | 13.6°C | -12.3°C | 159 mm | 92% | 1.5 m/s | 1.3 |
| 1995 | 0.2°C | -3.6°C | -7.5°C | 9.9°C | -15.1°C | 61 mm | 89% | 1.5 m/s | 1.7 |
| 1994 | 6.7°C | 2.4°C | -1.9°C | 17.1°C | -6.9°C | 70 mm | 85% | 1.3 m/s | 1.6 |
| 1993 | 3.2°C | -0.6°C | -4.4°C | 10.8°C | -12.1°C | 111 mm | 86% | 1.5 m/s | 1.4 |
| 1992 | 3.9°C | 0.4°C | -3.2°C | 16.1°C | -11.3°C | 99 mm | 87% | 1.5 m/s | 1.4 |
| 1991 | 5.3°C | 1.2°C | -2.8°C | 17.6°C | -11.2°C | 98 mm | 83% | 1.5 m/s | 1.6 |
| 1990 | 6.4°C | 2.0°C | -2.5°C | 16.2°C | -8.5°C | 149 mm | 87% | 1.5 m/s | 1.4 |
| 1989 ❄️ | -1.9°C | -5.9°C | -10.0°C | 6.8°C | -18.6°C | 38 mm | 83% | 1.5 m/s | 1.7 |
| 1988 | 3.3°C | -0.8°C | -4.9°C | 12.7°C | -14.3°C | 30 mm | 79% | 1.4 m/s | 1.6 |
| 1987 | 4.9°C | 1.1°C | -2.7°C | 11.9°C | -10.7°C | 49 mm | 85% | 1.5 m/s | 1.4 |
| 1986 | 4.3°C | 0.5°C | -3.2°C | 10.4°C | -7.3°C | 124 mm | 87% | 1.3 m/s | 1.5 |
| 1985 | 2.0°C | -1.9°C | -5.9°C | 9.3°C | -14.8°C | 34 mm | 84% | 1.5 m/s | 1.4 |
| 1984 | 6.8°C | 2.7°C | -1.4°C | 19.2°C | -8.1°C | 54 mm | 88% | 1.3 m/s | 1.4 |
| 1983 🌧️ | 0.6°C | -3.4°C | -7.5°C | 13.0°C | -25.6°C | 184 mm | 88% | 1.6 m/s | — |
| 1982 | 7.2°C | 3.0°C | -1.2°C | 21.3°C | -8.5°C | 49 mm | 86% | 1.4 m/s | — |
| 1981 | 1.3°C | -2.3°C | -5.9°C | 7.3°C | -17.3°C | 76 mm | 88% | 1.5 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 4.5°C with lows near -3.5°C (mean 0.5°C), based on 45 years of NASA POWER data.
December averages 87 mm of rainfall in Mechanicsburg, about average for rainfall. The wettest on record was 184 mm in 1983.
The hottest December reached 22.8°C in 2001. The coldest dipped to -25.6°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.9°C. Daytime highs moved from 3.6°C to 5.8°C and overnight lows from -4.4°C to -2.8°C over the same span.
December is one of the cooler months of the year in Mechanicsburg and about average for rainfall, so plan for around 4.5°C daytime highs and -3.5°C at night.
Not quite — December is the 3rd coolest month in Mechanicsburg, averaging 0.5°C.
For December in Mechanicsburg, pack warm layers and a jacket for chilly mornings, with typical highs of 4.5°C and lows of -3.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 85% — quite humid.
Average wind speed in December is 1.4 m/s. The windiest December on record averaged 1.9 m/s (2010).
The wettest December on record was 1983 with 184 mm. On average, December sees 87 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 Mechanicsburg 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.
