December is one of the cooler months of the year in Johnstown, with average highs near 2.3°C and lows around -5°C (mean -1.3°C). It is about average for rainfall, averaging 77 mm of rainfall and 87% relative humidity across the period.
December is one of the cooler months of the year in Johnstown. Across 45 years of records, the warmest December in Johnstown was 2015 — when the month averaged 5.4°C — while the coldest was 1989 at -8°C. Typical December days reach 2.3°C with nights near -5°C. The long-term trend is warming, about 0.5°C per decade.
December is about average for rainfall in Johnstown, averaging 77 mm of rainfall. The wettest December on record was 1990 with 165 mm, while the driest was 2017 at 32 mm.
Relative humidity in Johnstown during December averages 87%. The most humid December was 2005 at 93%, and the least humid was 1998 at 76%.
December receives about 1.4 kWh/m²/day of solar energy in Johnstown. The sunniest Decembers were 2000 and 2006 at 1.7 kWh/m²/day, and the cloudiest was 2007 at 1.1.
Average wind speed in Johnstown during December is 0.3 m/s. The windiest Decembers were 2017, 2020 and 2025, among others at 0.4 m/s, while the calmest were 2022, 2023 and 2024, among others at 0.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | -2.5°C | -0.9°C | -2.1°C | -0.6°C | -0.3°C | +2.2°C |
| Avg High | 1.1°C | 2.9°C | 1.6°C | 2.9°C | 3.6°C | +2.5°C |
| Avg Low | -6.1°C | -4.7°C | -5.9°C | -4.0°C | -4.2°C | +1.9°C |
| Avg Rain | 67 mm | 76 mm | 80 mm | 84 mm | 79 mm | +12 mm |
December temperatures in Johnstown have risen by about 1.8°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -23.6°C (1983) to a record high of 20.9°C (1998).
Rainfall in December is about average for rainfall, averaging 77 mm, with a wettest year of 165 mm.
A quieter season to visit Johnstown
If your dates are flexible, the more temperate months of July and August tend to be the most comfortable for visiting Johnstown. That said, December — with days averaging 2.3°C and nights around -5°C (mean -1.3°C) and moderate rainfall (77 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 | 1.2°C | -3.0°C | -7.2°C | 8.7°C | -14.8°C | 63 mm | 85% | 0.4 m/s | — |
| 2024 | 2.8°C | -0.9°C | -4.5°C | 13.0°C | -12.8°C | 82 mm | 87% | 0.3 m/s | 1.4 |
| 2023 | 6.0°C | 2.4°C | -1.2°C | 13.3°C | -6.5°C | 93 mm | 89% | 0.3 m/s | 1.3 |
| 2022 | 2.0°C | -2.0°C | -6.1°C | 12.9°C | -21.1°C | 80 mm | 89% | 0.3 m/s | 1.4 |
| 2021 | 7.5°C | 2.9°C | -1.6°C | 16.1°C | -8.1°C | 79 mm | 83% | 0.3 m/s | 1.6 |
| 2020 | 2.3°C | -1.1°C | -4.5°C | 14.2°C | -12.5°C | 76 mm | 88% | 0.4 m/s | 1.2 |
| 2019 | 3.6°C | -0.1°C | -3.9°C | 12.2°C | -15.1°C | 79 mm | 88% | 0.3 m/s | 1.4 |
| 2018 | 2.9°C | -0.3°C | -3.5°C | 11.0°C | -9.6°C | 121 mm | 92% | 0.3 m/s | 1.3 |
| 2017 | 0.4°C | -2.8°C | -6.0°C | 9.9°C | -14.5°C | 32 mm | 82% | 0.4 m/s | 1.5 |
| 2016 | 1.4°C | -2.2°C | -5.8°C | 11.0°C | -16.0°C | 83 mm | 86% | 0.4 m/s | 1.3 |
| 2015 🔥 | 9.5°C | 5.4°C | 1.4°C | 18.5°C | -5.5°C | 94 mm | 89% | 0.3 m/s | 1.2 |
| 2014 | 2.7°C | -0.4°C | -3.5°C | 11.9°C | -8.5°C | 66 mm | 87% | 0.3 m/s | 1.2 |
| 2013 | 1.7°C | -1.8°C | -5.4°C | 17.2°C | -11.9°C | 90 mm | 89% | 0.4 m/s | 1.2 |
| 2012 | 4.5°C | 1.1°C | -2.4°C | 17.9°C | -9.8°C | 123 mm | 92% | 0.4 m/s | 1.3 |
| 2011 | 4.3°C | 0.6°C | -3.2°C | 11.7°C | -9.5°C | 89 mm | 91% | 0.3 m/s | 1.4 |
| 2010 | -2.2°C | -5.2°C | -8.2°C | 12.3°C | -13.1°C | 64 mm | 90% | 0.4 m/s | 1.4 |
| 2009 | 0.2°C | -3.3°C | -6.9°C | 9.2°C | -13.0°C | 112 mm | 89% | 0.4 m/s | 1.4 |
| 2008 | 1.1°C | -2.8°C | -6.7°C | 10.3°C | -16.6°C | 147 mm | 87% | 0.4 m/s | 1.4 |
| 2007 | 2.4°C | -1.2°C | -4.8°C | 14.0°C | -14.6°C | 116 mm | 91% | 0.3 m/s | 1.1 |
| 2006 | 6.2°C | 1.8°C | -2.5°C | 19.8°C | -9.6°C | 46 mm | 84% | 0.3 m/s | 1.7 |
| 2005 | -1.4°C | -4.6°C | -7.9°C | 4.7°C | -15.3°C | 53 mm | 93% | 0.4 m/s | 1.4 |
| 2004 | 2.7°C | -1.3°C | -5.4°C | 12.1°C | -16.3°C | 67 mm | 87% | 0.3 m/s | 1.4 |
| 2003 | 1.3°C | -2.1°C | -5.5°C | 10.2°C | -11.3°C | 87 mm | 89% | 0.4 m/s | 1.4 |
| 2002 | 0.0°C | -3.5°C | -6.9°C | 8.8°C | -13.6°C | 69 mm | 89% | 0.4 m/s | 1.4 |
| 2001 | 5.8°C | 1.8°C | -2.1°C | 20.9°C | -10.4°C | 56 mm | 81% | 0.4 m/s | 1.5 |
| 2000 | -2.4°C | -6.2°C | -10.0°C | 5.2°C | -16.9°C | 47 mm | 85% | 0.4 m/s | 1.7 |
| 1999 | 3.2°C | -0.5°C | -4.2°C | 17.0°C | -12.0°C | 48 mm | 82% | 0.3 m/s | 1.4 |
| 1998 | 6.7°C | 2.0°C | -2.7°C | 20.9°C | -13.2°C | 38 mm | 76% | 0.3 m/s | 1.5 |
| 1997 | 1.9°C | -1.2°C | -4.3°C | 7.6°C | -10.8°C | 40 mm | 90% | 0.3 m/s | 1.5 |
| 1996 | 3.5°C | 0.0°C | -3.5°C | 14.4°C | -14.0°C | 93 mm | 92% | 0.3 m/s | 1.2 |
| 1995 | -1.8°C | -5.0°C | -8.1°C | 9.3°C | -15.3°C | 54 mm | 88% | 0.4 m/s | 1.6 |
| 1994 | 5.3°C | 0.9°C | -3.4°C | 14.6°C | -10.3°C | 69 mm | 86% | 0.3 m/s | 1.4 |
| 1993 | 1.1°C | -2.4°C | -6.0°C | 7.4°C | -15.7°C | 61 mm | 89% | 0.4 m/s | 1.3 |
| 1992 | 0.9°C | -2.5°C | -5.9°C | 12.6°C | -12.3°C | 106 mm | 91% | 0.3 m/s | 1.4 |
| 1991 | 3.3°C | -0.6°C | -4.6°C | 12.3°C | -13.9°C | 87 mm | 85% | 0.3 m/s | 1.4 |
| 1990 🌧️ | 4.6°C | 0.3°C | -4.0°C | 15.3°C | -12.7°C | 165 mm | 87% | 0.3 m/s | 1.4 |
| 1989 ❄️ | -4.4°C | -8.0°C | -11.5°C | 5.1°C | -18.1°C | 47 mm | 88% | 0.4 m/s | 1.6 |
| 1988 | 1.3°C | -2.5°C | -6.3°C | 8.4°C | -13.8°C | 46 mm | 80% | 0.3 m/s | 1.5 |
| 1987 | 2.5°C | -0.9°C | -4.3°C | 10.7°C | -12.3°C | 67 mm | 88% | 0.3 m/s | 1.3 |
| 1986 | 2.0°C | -1.5°C | -5.1°C | 11.7°C | -12.0°C | 80 mm | 89% | 0.3 m/s | 1.4 |
| 1985 | -0.6°C | -4.4°C | -8.2°C | 9.3°C | -17.7°C | 52 mm | 89% | 0.4 m/s | 1.3 |
| 1984 | 5.3°C | 1.5°C | -2.3°C | 17.2°C | -11.1°C | 83 mm | 89% | 0.3 m/s | 1.3 |
| 1983 | -2.4°C | -5.6°C | -8.9°C | 9.5°C | -23.6°C | 111 mm | 89% | 0.4 m/s | — |
| 1982 | 6.3°C | 2.2°C | -1.9°C | 17.8°C | -10.4°C | 52 mm | 85% | 0.3 m/s | — |
| 1981 | -0.2°C | -3.4°C | -6.5°C | 6.2°C | -16.1°C | 62 mm | 89% | 0.4 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 2.3°C with lows near -5°C (mean -1.3°C), based on 45 years of NASA POWER data.
December averages 77 mm of rainfall in Johnstown, about average for rainfall. The wettest on record was 165 mm in 1990.
The hottest December reached 20.9°C in 1998. The coldest dipped to -23.6°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.8°C. Daytime highs moved from 1.7°C to 3.9°C and overnight lows from -5.6°C to -4.1°C over the same span.
December is one of the cooler months of the year in Johnstown and about average for rainfall, so plan for around 2.3°C daytime highs and -5°C at night.
Not quite — December is the 3rd coolest month in Johnstown, averaging -1.3°C.
For December in Johnstown, pack warm layers and a jacket for chilly mornings, with typical highs of 2.3°C and lows of -5°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 87% — quite humid.
Average wind speed in December is 0.3 m/s. The windiest December on record averaged 0.4 m/s (1981).
The wettest December on record was 1990 with 165 mm. On average, December sees 77 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 Johnstown 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.
