December is one of the cooler months of the year in Rockford, with average highs near -0.4°C and lows around -8.5°C (mean -4.4°C). It is one of the drier months, averaging 50 mm of rainfall and 88% relative humidity across the period.
December is one of the cooler months of the year in Rockford. Across 45 years of records, the warmest December in Rockford was 2015 — when the month averaged 1.5°C — while the coldest was 1985 at -13.7°C. Typical December days reach -0.4°C with nights near -8.5°C. The long-term trend is warming, about 0.8°C per decade.
December is one of the drier months in Rockford, averaging 50 mm of rainfall. The wettest December on record was 2015 with 123 mm, while the driest was 1989 at 11 mm.
Relative humidity in Rockford during December averages 88%. The most humid December was 1985 at 96%, and the least humid was 1989 at 78%.
December receives about 1.4 kWh/m²/day of solar energy in Rockford. The sunniest Decembers were 1985 and 1998 at 1.7 kWh/m²/day, and the cloudiest was 1984 at 1.1.
Average wind speed in Rockford during December is 3.6 m/s. The windiest December was 2008 at 4.3 m/s, while the calmest was 1994 at 2.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | -6.7°C | -4.0°C | -4.9°C | -3.4°C | -2.7°C | +4°C |
| Avg High | -2.3°C | 0.0°C | -0.8°C | 0.4°C | 1.4°C | +3.7°C |
| Avg Low | -11.0°C | -8.0°C | -9.0°C | -7.2°C | -6.9°C | +4.1°C |
| Avg Rain | 53 mm | 38 mm | 59 mm | 52 mm | 51 mm | -2 mm |
December temperatures in Rockford have risen by about 4.4°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -37.8°C (1983) to a record high of 18.8°C (2012).
Rainfall in December is one of the drier months, averaging 50 mm, with a wettest year of 123 mm.
A quieter season to visit Rockford
If your dates are flexible, the more temperate months of July and August tend to be the most comfortable for visiting Rockford. That said, December — with days averaging -0.4°C and nights around -8.5°C (mean -4.4°C) and moderate rainfall (50 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 | -1.5°C | -6.8°C | -12.0°C | 10.1°C | -25.6°C | 50 mm | 87% | 3.7 m/s | — |
| 2024 | 1.3°C | -2.7°C | -6.7°C | 10.5°C | -17.9°C | 30 mm | 84% | 3.5 m/s | 1.4 |
| 2023 | 4.5°C | 1.1°C | -2.3°C | 13.2°C | -8.2°C | 61 mm | 87% | 3.1 m/s | 1.2 |
| 2022 | -1.2°C | -5.2°C | -9.3°C | 9.8°C | -24.4°C | 61 mm | 88% | 4 m/s | 1.3 |
| 2021 | 4.0°C | -0.3°C | -4.5°C | 17.6°C | -11.7°C | 55 mm | 81% | 3.7 m/s | 1.5 |
| 2020 | 1.3°C | -2.6°C | -6.5°C | 9.8°C | -12.8°C | 47 mm | 87% | 3.3 m/s | 1.5 |
| 2019 | 2.6°C | -1.2°C | -5.0°C | 11.2°C | -15.9°C | 43 mm | 89% | 3.6 m/s | 1.6 |
| 2018 | 1.3°C | -2.3°C | -5.9°C | 7.3°C | -13.6°C | 66 mm | 91% | 3 m/s | 1.4 |
| 2017 | -1.5°C | -5.1°C | -8.8°C | 15.0°C | -23.1°C | 13 mm | 80% | 3.8 m/s | 1.6 |
| 2016 | -2.7°C | -6.7°C | -10.7°C | 5.4°C | -30.9°C | 48 mm | 89% | 3.8 m/s | 1.5 |
| 2015 🔥 🌧️ | 4.9°C | 1.5°C | -1.9°C | 15.2°C | -13.1°C | 123 mm | 90% | 3.9 m/s | 1.2 |
| 2014 | 0.7°C | -2.6°C | -5.9°C | 7.2°C | -19.3°C | 21 mm | 87% | 3.1 m/s | 1.2 |
| 2013 | -3.7°C | -7.9°C | -12.0°C | 9.3°C | -20.9°C | 39 mm | 88% | 3.5 m/s | 1.5 |
| 2012 | 2.7°C | -1.5°C | -5.8°C | 18.8°C | -17.7°C | 67 mm | 89% | 3.3 m/s | 1.3 |
| 2011 | 3.1°C | -0.8°C | -4.6°C | 9.0°C | -14.1°C | 58 mm | 85% | 3.4 m/s | 1.5 |
| 2010 | -3.4°C | -7.5°C | -11.6°C | 8.6°C | -22.4°C | 43 mm | 93% | 3.4 m/s | 1.4 |
| 2009 | -2.1°C | -6.1°C | -10.2°C | 10.0°C | -22.5°C | 86 mm | 93% | 3.5 m/s | 1.4 |
| 2008 | -3.7°C | -8.9°C | -14.2°C | 6.5°C | -25.7°C | 114 mm | 90% | 4.3 m/s | 1.4 |
| 2007 | -2.2°C | -6.3°C | -10.4°C | 3.9°C | -21.8°C | 104 mm | 95% | 3.2 m/s | 1.2 |
| 2006 | 2.9°C | -1.7°C | -6.3°C | 11.8°C | -23.3°C | 62 mm | 90% | 3.7 m/s | 1.4 |
| 2005 | -3.0°C | -6.3°C | -9.7°C | 3.9°C | -19.7°C | 28 mm | 90% | 3.3 m/s | 1.5 |
| 2004 | 0.7°C | -3.3°C | -7.3°C | 10.7°C | -21.4°C | 25 mm | 82% | 4.2 m/s | 1.5 |
| 2003 | 1.7°C | -2.2°C | -6.0°C | 7.5°C | -15.9°C | 65 mm | 85% | 3.7 m/s | 1.5 |
| 2002 | 1.4°C | -2.4°C | -6.3°C | 9.7°C | -14.0°C | 21 mm | 83% | 3.8 m/s | 1.6 |
| 2001 | 3.1°C | -0.7°C | -4.5°C | 18.7°C | -16.1°C | 30 mm | 85% | 3.6 m/s | 1.5 |
| 2000 | -6.4°C | -11.0°C | -15.6°C | 2.3°C | -25.7°C | 56 mm | 92% | 3.2 m/s | 1.5 |
| 1999 | 1.1°C | -3.2°C | -7.6°C | 11.9°C | -19.5°C | 43 mm | 84% | 3.3 m/s | 1.3 |
| 1998 | 3.4°C | -1.1°C | -5.6°C | 18.0°C | -20.2°C | 23 mm | 83% | 3.5 m/s | 1.7 |
| 1997 | 0.7°C | -2.6°C | -6.0°C | 5.5°C | -13.8°C | 30 mm | 89% | 3.2 m/s | 1.6 |
| 1996 | -1.5°C | -5.2°C | -8.8°C | 4.2°C | -20.5°C | 42 mm | 88% | 3.5 m/s | 1.3 |
| 1995 | -2.0°C | -6.1°C | -10.2°C | 6.3°C | -20.5°C | 17 mm | 85% | 3.7 m/s | 1.6 |
| 1994 | 1.6°C | -2.2°C | -6.1°C | 12.0°C | -17.8°C | 28 mm | 92% | 2.9 m/s | 1.5 |
| 1993 | -0.9°C | -4.0°C | -7.2°C | 6.5°C | -21.0°C | 26 mm | 86% | 3.5 m/s | 1.4 |
| 1992 | -1.5°C | -5.7°C | -9.8°C | 3.1°C | -24.4°C | 75 mm | 91% | 3.5 m/s | 1.4 |
| 1991 | 0.8°C | -3.7°C | -8.2°C | 14.1°C | -18.1°C | 40 mm | 89% | 3.5 m/s | 1.5 |
| 1990 | -1.6°C | -6.3°C | -11.0°C | 6.5°C | -29.8°C | 58 mm | 88% | 4 m/s | 1.6 |
| 1989 | -6.0°C | -10.2°C | -14.4°C | 6.3°C | -28.2°C | 11 mm | 78% | 3.7 m/s | 1.6 |
| 1988 | -0.7°C | -5.3°C | -10.0°C | 7.6°C | -22.3°C | 44 mm | 83% | 4.1 m/s | 1.5 |
| 1987 | -0.2°C | -4.3°C | -8.3°C | 6.1°C | -20.5°C | 97 mm | 91% | 3.8 m/s | 1.2 |
| 1986 | -0.4°C | -4.1°C | -7.8°C | 4.0°C | -21.4°C | 20 mm | 91% | 3.3 m/s | 1.3 |
| 1985 ❄️ | -8.1°C | -13.7°C | -19.3°C | 0.9°C | -30.0°C | 48 mm | 96% | 3.8 m/s | 1.7 |
| 1984 | 1.3°C | -3.0°C | -7.2°C | 16.2°C | -21.2°C | 81 mm | 87% | 4.2 m/s | 1.1 |
| 1983 | -8.3°C | -13.0°C | -17.7°C | 2.8°C | -37.8°C | 59 mm | 94% | 3.6 m/s | — |
| 1982 | 3.3°C | -1.0°C | -5.4°C | 18.2°C | -15.2°C | 99 mm | 88% | 4 m/s | — |
| 1981 | -1.6°C | -5.4°C | -9.2°C | 5.0°C | -17.4°C | 18 mm | 88% | 3.3 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around -0.4°C with lows near -8.5°C (mean -4.4°C), based on 45 years of NASA POWER data.
December averages 50 mm of rainfall in Rockford, one of the drier months. The wettest on record was 123 mm in 2015.
The hottest December reached 18.8°C in 2012. The coldest dipped to -37.8°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 4.4°C. Daytime highs moved from -2.7°C to 1.4°C and overnight lows from -11.8°C to -7°C over the same span.
December is one of the cooler months of the year in Rockford and one of the drier months, so plan for around -0.4°C daytime highs and -8.5°C at night.
Not quite — December is the 3rd coolest month in Rockford, averaging -4.4°C.
For December in Rockford, pack warm layers and a jacket for chilly mornings, with typical highs of -0.4°C and lows of -8.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 88% — quite humid.
Average wind speed in December is 3.6 m/s. The windiest December on record averaged 4.3 m/s (2008).
The wettest December on record was 2015 with 123 mm. On average, December sees 50 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 Rockford 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.
