December is one of the cooler months of the year in Allentown, with average highs near 4.2°C and lows around -3.9°C (mean 0.2°C). It is about average for rainfall, averaging 96 mm of rainfall and 86% relative humidity across the period.
December is one of the cooler months of the year in Allentown. Across 45 years of records, the warmest December in Allentown was 2015 — when the month averaged 7.2°C — while the coldest was 1989 at -6.3°C. Typical December days reach 4.2°C with nights near -3.9°C. The long-term trend is warming, about 0.5°C per decade.
December is about average for rainfall in Allentown, averaging 96 mm of rainfall. The wettest December on record was 2023 with 228 mm, while the driest was 1998 at 19 mm.
Relative humidity in Allentown during December averages 86%. The most humid December was 1996 at 93%, and the least humid was 1998 at 78%.
December receives about 1.6 kWh/m²/day of solar energy in Allentown. The sunniest Decembers were 2000 and 2001 at 1.9 kWh/m²/day, and the cloudiest were 1992 and 2014 at 1.3.
Average wind speed in Allentown during December is 0.6 m/s. The windiest December was 2010 at 0.8 m/s, while the calmest were 1988, 2021 and 2023, among others at 0.5 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | -1.2°C | 0.5°C | -0.4°C | 1.1°C | 0.9°C | +2.1°C |
| Avg High | 2.8°C | 4.7°C | 3.7°C | 5.0°C | 5.1°C | +2.3°C |
| Avg Low | -5.2°C | -3.6°C | -4.5°C | -2.8°C | -3.3°C | +1.9°C |
| Avg Rain | 74 mm | 94 mm | 108 mm | 98 mm | 111 mm | +37 mm |
December temperatures in Allentown have risen by about 1.8°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -21.1°C (1983) to a record high of 21.8°C (2001).
Rainfall in December is about average for rainfall, averaging 96 mm, with a wettest year of 228 mm.
A quieter season to visit Allentown
If your dates are flexible, the more temperate months of August and June tend to be the most comfortable for visiting Allentown. That said, December — with days averaging 4.2°C and nights around -3.9°C (mean 0.2°C) and higher rainfall (96 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 | 1.8°C | -2.2°C | -6.2°C | 10.2°C | -13.0°C | 73 mm | 82% | 0.7 m/s | — |
| 2024 | 4.5°C | 0.3°C | -3.9°C | 16.3°C | -14.1°C | 99 mm | 83% | 0.6 m/s | 1.7 |
| 2023 🌧️ | 7.4°C | 3.3°C | -0.8°C | 13.8°C | -5.9°C | 228 mm | 90% | 0.5 m/s | 1.4 |
| 2022 | 4.5°C | 0.0°C | -4.4°C | 13.2°C | -15.9°C | 115 mm | 86% | 0.6 m/s | 1.7 |
| 2021 | 8.3°C | 3.7°C | -0.9°C | 16.8°C | -6.2°C | 36 mm | 85% | 0.5 m/s | 1.7 |
| 2020 | 4.2°C | 0.2°C | -3.9°C | 15.8°C | -15.2°C | 115 mm | 89% | 0.6 m/s | 1.6 |
| 2019 | 4.1°C | 0.3°C | -3.5°C | 12.8°C | -12.6°C | 116 mm | 89% | 0.6 m/s | 1.5 |
| 2018 | 5.4°C | 1.6°C | -2.3°C | 16.1°C | -8.0°C | 153 mm | 90% | 0.6 m/s | 1.5 |
| 2017 | 2.6°C | -1.3°C | -5.1°C | 14.1°C | -15.6°C | 41 mm | 80% | 0.6 m/s | 1.6 |
| 2016 | 3.9°C | -0.1°C | -4.0°C | 14.9°C | -12.2°C | 72 mm | 83% | 0.6 m/s | 1.6 |
| 2015 🔥 | 11.3°C | 7.2°C | 3.1°C | 19.9°C | -5.0°C | 117 mm | 88% | 0.6 m/s | 1.4 |
| 2014 | 5.0°C | 1.4°C | -2.3°C | 14.4°C | -5.9°C | 84 mm | 87% | 0.6 m/s | 1.3 |
| 2013 | 3.5°C | -0.5°C | -4.5°C | 19.4°C | -12.5°C | 105 mm | 91% | 0.6 m/s | 1.4 |
| 2012 | 6.4°C | 2.5°C | -1.4°C | 17.0°C | -8.3°C | 109 mm | 89% | 0.6 m/s | 1.4 |
| 2011 | 7.0°C | 2.6°C | -1.7°C | 14.6°C | -5.6°C | 105 mm | 90% | 0.6 m/s | 1.7 |
| 2010 | 1.1°C | -2.4°C | -5.9°C | 15.7°C | -9.5°C | 74 mm | 82% | 0.8 m/s | 1.7 |
| 2009 | 2.8°C | -1.0°C | -4.8°C | 17.0°C | -12.0°C | 152 mm | 86% | 0.7 m/s | 1.6 |
| 2008 | 3.5°C | -0.8°C | -5.1°C | 15.1°C | -19.6°C | 165 mm | 90% | 0.6 m/s | 1.5 |
| 2007 | 2.5°C | -0.8°C | -4.2°C | 13.6°C | -14.6°C | 127 mm | 91% | 0.6 m/s | 1.4 |
| 2006 | 7.9°C | 3.2°C | -1.4°C | 20.5°C | -8.1°C | 61 mm | 86% | 0.6 m/s | 1.8 |
| 2005 | 1.7°C | -2.3°C | -6.2°C | 9.1°C | -16.2°C | 90 mm | 89% | 0.6 m/s | 1.6 |
| 2004 | 4.5°C | 0.2°C | -4.0°C | 13.7°C | -15.2°C | 101 mm | 87% | 0.6 m/s | 1.6 |
| 2003 | 3.6°C | -0.4°C | -4.3°C | 10.9°C | -10.5°C | 122 mm | 88% | 0.7 m/s | 1.6 |
| 2002 | 1.6°C | -2.3°C | -6.2°C | 11.5°C | -11.9°C | 116 mm | 90% | 0.6 m/s | 1.6 |
| 2001 | 8.2°C | 3.5°C | -1.2°C | 21.8°C | -9.4°C | 47 mm | 80% | 0.6 m/s | 1.9 |
| 2000 | 0.9°C | -3.4°C | -7.8°C | 15.1°C | -15.1°C | 99 mm | 80% | 0.7 m/s | 1.9 |
| 1999 | 5.5°C | 1.1°C | -3.3°C | 16.4°C | -11.5°C | 61 mm | 83% | 0.6 m/s | 1.7 |
| 1998 | 8.0°C | 3.1°C | -1.8°C | 21.1°C | -10.7°C | 19 mm | 78% | 0.6 m/s | 1.6 |
| 1997 | 4.5°C | 0.4°C | -3.6°C | 9.5°C | -11.8°C | 66 mm | 87% | 0.6 m/s | 1.7 |
| 1996 | 4.5°C | 1.2°C | -2.1°C | 13.2°C | -11.5°C | 193 mm | 93% | 0.6 m/s | 1.5 |
| 1995 | -0.1°C | -4.1°C | -8.0°C | 8.4°C | -14.7°C | 59 mm | 90% | 0.6 m/s | 1.8 |
| 1994 | 6.4°C | 1.9°C | -2.6°C | 16.1°C | -8.1°C | 74 mm | 86% | 0.6 m/s | 1.6 |
| 1993 | 3.1°C | -0.8°C | -4.7°C | 10.6°C | -12.7°C | 125 mm | 86% | 0.7 m/s | 1.5 |
| 1992 | 3.7°C | 0.0°C | -3.8°C | 13.0°C | -11.7°C | 88 mm | 87% | 0.7 m/s | 1.3 |
| 1991 | 5.2°C | 0.9°C | -3.3°C | 17.3°C | -11.1°C | 92 mm | 83% | 0.6 m/s | 1.7 |
| 1990 | 6.2°C | 1.7°C | -2.8°C | 16.2°C | -9.3°C | 162 mm | 87% | 0.6 m/s | 1.5 |
| 1989 ❄️ | -2.0°C | -6.3°C | -10.6°C | 6.3°C | -18.0°C | 35 mm | 82% | 0.6 m/s | 1.8 |
| 1988 | 3.0°C | -1.2°C | -5.4°C | 12.0°C | -15.1°C | 27 mm | 81% | 0.5 m/s | 1.7 |
| 1987 | 4.3°C | 0.6°C | -3.2°C | 12.0°C | -12.1°C | 42 mm | 87% | 0.6 m/s | 1.5 |
| 1986 | 4.1°C | 0.3°C | -3.6°C | 9.8°C | -8.9°C | 121 mm | 88% | 0.6 m/s | 1.6 |
| 1985 | 1.7°C | -2.3°C | -6.4°C | 9.1°C | -13.7°C | 40 mm | 85% | 0.6 m/s | 1.6 |
| 1984 | 6.1°C | 2.1°C | -1.9°C | 17.6°C | -7.6°C | 70 mm | 90% | 0.5 m/s | 1.6 |
| 1983 | 0.5°C | -3.2°C | -7.0°C | 13.5°C | -21.1°C | 202 mm | 89% | 0.7 m/s | — |
| 1982 | 6.6°C | 2.4°C | -1.9°C | 19.8°C | -10.8°C | 51 mm | 87% | 0.5 m/s | — |
| 1981 | 0.8°C | -2.9°C | -6.6°C | 6.4°C | -17.9°C | 80 mm | 90% | 0.6 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 4.2°C with lows near -3.9°C (mean 0.2°C), based on 45 years of NASA POWER data.
December averages 96 mm of rainfall in Allentown, about average for rainfall. The wettest on record was 228 mm in 2023.
The hottest December reached 21.8°C in 2001. The coldest dipped to -21.1°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.8°C. Daytime highs moved from 3.1°C to 5.3°C and overnight lows from -4.8°C to -3.2°C over the same span.
December is one of the cooler months of the year in Allentown and about average for rainfall, so plan for around 4.2°C daytime highs and -3.9°C at night.
Not quite — December is the 3rd coolest month in Allentown, averaging 0.2°C.
For December in Allentown, pack warm layers and a jacket for chilly mornings, with typical highs of 4.2°C and lows of -3.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 86% — quite humid.
Average wind speed in December is 0.6 m/s. The windiest December on record averaged 0.8 m/s (2010).
The wettest December on record was 2023 with 228 mm. On average, December sees 96 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 Allentown 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.
