December is one of the cooler months of the year in Decatur, with average highs near 11.2°C and lows around 0.8°C (mean 6°C). It is a relatively wet time of year, averaging 140 mm of rainfall and 84% relative humidity across the period.
December is one of the cooler months of the year in Decatur. Across 45 years of records, the warmest December in Decatur was 2015 — when the month averaged 11.7°C — while the coldest was 1989 at -0.3°C. Typical December days reach 11.2°C with nights near 0.8°C. The long-term trend is warming, about 0.7°C per decade.
December is a relatively wet time of year in Decatur, averaging 140 mm of rainfall. The wettest December on record was 1990 with 349 mm, while the driest was 2025 at 49 mm.
Relative humidity in Decatur during December averages 84%. The most humid December was 2018 at 89%, and the least humid were 1999 and 2023 at 77%.
December receives about 2.2 kWh/m²/day of solar energy in Decatur. The sunniest Decembers were 2001, 2004 and 2023, among others at 2.5 kWh/m²/day, and the cloudiest was 1992 at 1.7.
Average wind speed in Decatur during December is 1.2 m/s. The windiest Decembers were 1982, 1983 and 2008 at 1.4 m/s, while the calmest was 1986 at 1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 4.6°C | 6.2°C | 5.3°C | 7.0°C | 7.5°C | +2.9°C |
| Avg High | 9.5°C | 11.3°C | 10.5°C | 12.0°C | 13.0°C | +3.5°C |
| Avg Low | -0.4°C | 1.0°C | 0.0°C | 2.0°C | 2.0°C | +2.4°C |
| Avg Rain | 126 mm | 150 mm | 132 mm | 164 mm | 120 mm | -5 mm |
December temperatures in Decatur have risen by about 3°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -18.7°C (1989) to a record high of 24.5°C (1998).
Rainfall in December is a relatively wet time of year, averaging 140 mm, with a wettest year of 349 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.8°C per decade while lows rose 0.6°C per decade, widening the gap between day and night.
A quieter season to visit Decatur
If your dates are flexible, the more temperate months of September and May tend to be the most comfortable for visiting Decatur. That said, December — with days averaging 11.2°C and nights around 0.8°C (mean 6°C) and higher rainfall (140 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 | 12.7°C | 6.8°C | 0.9°C | 22.8°C | -7.9°C | 49 mm | 78% | 1.1 m/s | — |
| 2024 | 12.5°C | 7.1°C | 1.7°C | 20.9°C | -6.7°C | 111 mm | 79% | 1.3 m/s | 2.3 |
| 2023 | 13.4°C | 7.6°C | 1.7°C | 22.1°C | -5.6°C | 122 mm | 77% | 1.1 m/s | 2.5 |
| 2022 | 11.6°C | 6.8°C | 2.0°C | 22.9°C | -14.6°C | 179 mm | 85% | 1.2 m/s | 2 |
| 2021 | 17.0°C | 11.5°C | 5.9°C | 23.1°C | -2.6°C | 132 mm | 86% | 1.2 m/s | 2 |
| 2020 | 10.9°C | 5.3°C | -0.4°C | 18.8°C | -7.2°C | 127 mm | 85% | 1.1 m/s | 2.4 |
| 2019 | 13.7°C | 8.7°C | 3.7°C | 21.4°C | -4.9°C | 193 mm | 87% | 1.2 m/s | 2.2 |
| 2018 | 10.8°C | 6.6°C | 2.4°C | 20.0°C | -5.3°C | 228 mm | 89% | 1.1 m/s | 1.9 |
| 2017 | 10.5°C | 5.4°C | 0.3°C | 20.8°C | -8.4°C | 124 mm | 80% | 1.1 m/s | 2.2 |
| 2016 | 12.1°C | 6.6°C | 1.0°C | 22.5°C | -9.0°C | 129 mm | 82% | 1.3 m/s | 2.1 |
| 2015 🔥 | 16.5°C | 11.7°C | 7.0°C | 23.7°C | -3.6°C | 288 mm | 87% | 1.2 m/s | 2.1 |
| 2014 | 11.8°C | 7.1°C | 2.4°C | 20.3°C | -4.1°C | 146 mm | 88% | 1.1 m/s | 1.9 |
| 2013 | 11.2°C | 6.0°C | 0.8°C | 23.8°C | -6.2°C | 167 mm | 84% | 1.1 m/s | 2 |
| 2012 | 14.3°C | 8.7°C | 3.1°C | 21.6°C | -5.5°C | 156 mm | 83% | 1.2 m/s | 2 |
| 2011 | 12.4°C | 7.2°C | 2.1°C | 19.3°C | -4.8°C | 155 mm | 85% | 1.1 m/s | 2.2 |
| 2010 | 6.7°C | 1.9°C | -2.9°C | 17.2°C | -12.2°C | 59 mm | 79% | 1.3 m/s | 2.3 |
| 2009 | 8.6°C | 4.0°C | -0.7°C | 19.0°C | -5.3°C | 181 mm | 88% | 1.2 m/s | 2 |
| 2008 | 11.0°C | 5.8°C | 0.6°C | 20.5°C | -9.5°C | 249 mm | 83% | 1.4 m/s | 2 |
| 2007 | 14.4°C | 8.8°C | 3.3°C | 23.8°C | -5.2°C | 61 mm | 81% | 1.2 m/s | 2.2 |
| 2006 | 13.4°C | 7.4°C | 1.5°C | 20.2°C | -7.9°C | 89 mm | 83% | 1.2 m/s | 2.4 |
| 2005 | 8.8°C | 3.3°C | -2.2°C | 17.6°C | -7.0°C | 106 mm | 83% | 1.1 m/s | 2.3 |
| 2004 | 9.9°C | 4.9°C | -0.1°C | 19.7°C | -8.0°C | 172 mm | 85% | 1.3 m/s | 2.5 |
| 2003 | 10.2°C | 4.4°C | -1.4°C | 15.1°C | -5.5°C | 83 mm | 80% | 1.3 m/s | 2.4 |
| 2002 | 10.0°C | 5.2°C | 0.4°C | 17.4°C | -5.4°C | 164 mm | 86% | 1.3 m/s | 2.2 |
| 2001 | 12.9°C | 7.7°C | 2.5°C | 21.5°C | -6.0°C | 138 mm | 84% | 1.2 m/s | 2.5 |
| 2000 | 6.2°C | 1.0°C | -4.2°C | 20.0°C | -10.3°C | 75 mm | 81% | 1.2 m/s | 2.2 |
| 1999 | 12.8°C | 6.4°C | 0.1°C | 20.6°C | -6.5°C | 65 mm | 77% | 1.2 m/s | 2.4 |
| 1998 | 12.7°C | 7.4°C | 2.2°C | 24.5°C | -11.9°C | 171 mm | 85% | 1.2 m/s | 1.9 |
| 1997 | 9.1°C | 4.6°C | 0.0°C | 15.9°C | -5.5°C | 98 mm | 87% | 1.1 m/s | 2.1 |
| 1996 | 12.0°C | 6.8°C | 1.6°C | 20.8°C | -7.4°C | 119 mm | 86% | 1.3 m/s | 2.2 |
| 1995 | 8.7°C | 3.9°C | -0.9°C | 18.9°C | -9.7°C | 111 mm | 84% | 1.2 m/s | 2.2 |
| 1994 | 12.6°C | 7.6°C | 2.6°C | 19.3°C | -4.4°C | 97 mm | 87% | 1.1 m/s | 2.1 |
| 1993 | 9.9°C | 5.0°C | 0.2°C | 18.1°C | -7.4°C | 135 mm | 84% | 1.2 m/s | 2.1 |
| 1992 | 9.8°C | 5.3°C | 0.8°C | 17.7°C | -4.5°C | 144 mm | 88% | 1.1 m/s | 1.7 |
| 1991 | 12.2°C | 6.9°C | 1.6°C | 23.2°C | -5.4°C | 213 mm | 87% | 1.1 m/s | 2.3 |
| 1990 🌧️ | 13.3°C | 7.7°C | 2.1°C | 21.8°C | -8.8°C | 349 mm | 85% | 1.3 m/s | 1.9 |
| 1989 ❄️ | 4.5°C | -0.3°C | -5.2°C | 17.1°C | -18.7°C | 96 mm | 84% | 1.3 m/s | 2.3 |
| 1988 | 10.7°C | 5.0°C | -0.7°C | 18.8°C | -5.5°C | 110 mm | 83% | 1.2 m/s | 2.4 |
| 1987 | 12.7°C | 7.2°C | 1.7°C | 21.6°C | -5.3°C | 126 mm | 82% | 1.3 m/s | 2.1 |
| 1986 | 9.0°C | 4.4°C | -0.2°C | 18.2°C | -4.4°C | 110 mm | 89% | 1 m/s | 1.9 |
| 1985 | 7.2°C | 2.0°C | -3.2°C | 19.4°C | -12.0°C | 68 mm | 80% | 1.1 m/s | 2.5 |
| 1984 | 15.1°C | 10.1°C | 5.1°C | 21.9°C | -7.3°C | 65 mm | 89% | 1.1 m/s | 2 |
| 1983 | 6.5°C | 1.7°C | -3.1°C | 21.2°C | -17.8°C | 258 mm | 86% | 1.4 m/s | — |
| 1982 | 12.6°C | 8.3°C | 4.0°C | 22.4°C | -6.1°C | 183 mm | 88% | 1.4 m/s | — |
| 1981 | 7.6°C | 2.7°C | -2.1°C | 17.1°C | -12.7°C | 113 mm | 82% | 1.2 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 11.2°C with lows near 0.8°C (mean 6°C), based on 45 years of NASA POWER data.
December averages 140 mm of rainfall in Decatur, a relatively wet time of year. The wettest on record was 349 mm in 1990.
The hottest December reached 24.5°C in 1998. The coldest dipped to -18.7°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 3°C. Daytime highs moved from 9.8°C to 13.4°C and overnight lows from 0.1°C to 2.4°C over the same span.
December is one of the cooler months of the year in Decatur and a relatively wet time of year, so plan for around 11.2°C daytime highs and 0.8°C at night.
Not quite — December is the 2nd coolest month in Decatur, averaging 6°C.
For December in Decatur, pack warm layers and a jacket for chilly mornings, with typical highs of 11.2°C and lows of 0.8°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 84% — quite humid.
Average wind speed in December is 1.2 m/s. The windiest December on record averaged 1.4 m/s (1982).
The wettest December on record was 1990 with 349 mm. On average, December sees 140 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 Decatur 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.
