December is one of the cooler months of the year in Sidney, with average highs near 6.5°C and lows around 3.5°C (mean 5°C). It is a relatively wet time of year, averaging 141 mm of rainfall and 86% relative humidity across the period.
December is one of the cooler months of the year in Sidney. Across 45 years of records, the warmest December in Sidney was 2023 — when the month averaged 7.6°C — while the coldest was 1983 at 1.7°C. Typical December days reach 6.5°C with nights near 3.5°C. The long-term trend is warming, about 0.3°C per decade.
December is a relatively wet time of year in Sidney, averaging 141 mm of rainfall. The wettest December on record was 2025 with 241 mm, while the driest was 1985 at 38 mm.
Relative humidity in Sidney during December averages 86%. The most humid December was 2024 at 92%, and the least humid was 2009 at 81%.
December receives about 0.8 kWh/m²/day of solar energy in Sidney. The sunniest December was 2009 at 1 kWh/m²/day, and the cloudiest were 2012 and 2019 at 0.6.
Average wind speed in Sidney during December is 3.1 m/s. The windiest December was 1992 at 3.8 m/s, while the calmest was 1989 at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 4.4°C | 4.9°C | 5.2°C | 5.2°C | 5.5°C | +1.1°C |
| Avg High | 5.9°C | 6.5°C | 6.7°C | 6.6°C | 7.0°C | +1.1°C |
| Avg Low | 2.9°C | 3.3°C | 3.7°C | 3.9°C | 4.0°C | +1.1°C |
| Avg Rain | 124 mm | 152 mm | 126 mm | 137 mm | 179 mm | +55 mm |
December temperatures in Sidney have risen by about 1.7°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -10.4°C (1990) to a record high of 13.8°C (2014).
Rainfall in December is a relatively wet time of year, averaging 141 mm, with a wettest year of 241 mm.
A quieter season to visit Sidney
If your dates are flexible, the more temperate months of August and July tend to be the most comfortable for visiting Sidney. That said, December — with days averaging 6.5°C and nights around 3.5°C (mean 5°C) and higher rainfall (141 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 🌧️ | 7.7°C | 6.3°C | 4.9°C | 13.6°C | -0.2°C | 241 mm | 91% | 3.1 m/s | — |
| 2024 | 7.4°C | 6.1°C | 4.7°C | 9.6°C | 2.6°C | 169 mm | 92% | 3.5 m/s | 0.8 |
| 2023 🔥 | 9.1°C | 7.6°C | 6.1°C | 12.5°C | 2.5°C | 165 mm | 91% | 2.9 m/s | 0.7 |
| 2022 | 5.1°C | 3.5°C | 1.9°C | 9.6°C | -8.1°C | 160 mm | 89% | 3.2 m/s | 0.8 |
| 2021 | 4.6°C | 3.0°C | 1.4°C | 12.0°C | -9.7°C | 149 mm | 87% | 3.2 m/s | 0.8 |
| 2020 | 8.0°C | 6.5°C | 5.0°C | 11.0°C | 1.6°C | 191 mm | 89% | 3.1 m/s | 0.8 |
| 2019 | 7.5°C | 6.2°C | 5.0°C | 10.3°C | 2.4°C | 128 mm | 91% | 2.5 m/s | 0.6 |
| 2018 | 7.8°C | 6.3°C | 4.8°C | 12.2°C | 1.3°C | 169 mm | 85% | 3.4 m/s | 0.8 |
| 2017 | 6.3°C | 4.8°C | 3.3°C | 8.9°C | -0.8°C | 134 mm | 85% | 2.7 m/s | 0.9 |
| 2016 | 4.5°C | 3.2°C | 1.8°C | 9.2°C | -4.4°C | 132 mm | 83% | 3.2 m/s | 0.8 |
| 2015 | 7.1°C | 5.8°C | 4.5°C | 12.5°C | -0.1°C | 224 mm | 87% | 3.5 m/s | 0.7 |
| 2014 | 7.9°C | 6.4°C | 4.9°C | 13.8°C | -1.3°C | 134 mm | 86% | 3.2 m/s | 0.9 |
| 2013 | 5.0°C | 3.7°C | 2.3°C | 9.8°C | -5.3°C | 66 mm | 84% | 2.3 m/s | 0.8 |
| 2012 | 6.5°C | 5.4°C | 4.2°C | 9.8°C | 1.8°C | 145 mm | 88% | 3.2 m/s | 0.6 |
| 2011 | 6.0°C | 4.8°C | 3.6°C | 10.3°C | 1.0°C | 72 mm | 87% | 2.3 m/s | 0.8 |
| 2010 | 7.3°C | 5.8°C | 4.3°C | 10.9°C | -1.1°C | 164 mm | 86% | 3.6 m/s | 0.8 |
| 2009 | 5.1°C | 3.7°C | 2.3°C | 10.7°C | -2.3°C | 62 mm | 81% | 2.9 m/s | 1 |
| 2008 | 4.4°C | 2.8°C | 1.1°C | 10.8°C | -7.6°C | 123 mm | 86% | 3.2 m/s | 0.7 |
| 2007 | 6.2°C | 4.8°C | 3.4°C | 13.3°C | -0.1°C | 177 mm | 87% | 3.4 m/s | 0.7 |
| 2006 | 7.2°C | 5.7°C | 4.2°C | 11.3°C | 1.0°C | 135 mm | 86% | 3.4 m/s | 0.7 |
| 2005 | 7.2°C | 5.8°C | 4.4°C | 13.6°C | -0.3°C | 131 mm | 84% | 3 m/s | 0.8 |
| 2004 | 7.8°C | 6.4°C | 5.0°C | 12.5°C | 2.8°C | 151 mm | 89% | 2.7 m/s | 0.7 |
| 2003 | 7.0°C | 5.5°C | 4.1°C | 10.4°C | -0.2°C | 100 mm | 88% | 3.3 m/s | 0.7 |
| 2002 | 8.4°C | 6.8°C | 5.1°C | 13.6°C | 2.5°C | 129 mm | 87% | 3.3 m/s | 0.7 |
| 2001 | 7.0°C | 5.3°C | 3.6°C | 10.1°C | 0.7°C | 165 mm | 87% | 3.7 m/s | 0.8 |
| 2000 | 6.4°C | 4.9°C | 3.5°C | 10.0°C | -0.6°C | 89 mm | 86% | 3 m/s | 0.9 |
| 1999 | 7.7°C | 6.3°C | 4.8°C | 11.8°C | 2.0°C | 152 mm | 87% | 3 m/s | 0.7 |
| 1998 | 6.4°C | 5.0°C | 3.5°C | 11.9°C | -6.1°C | 203 mm | 86% | 3.5 m/s | 0.7 |
| 1997 | 7.9°C | 6.3°C | 4.7°C | 11.4°C | 2.9°C | 106 mm | 88% | 3.2 m/s | 0.8 |
| 1996 | 5.1°C | 3.5°C | 1.9°C | 9.4°C | -5.6°C | 213 mm | 88% | 3.7 m/s | 0.7 |
| 1995 | 7.0°C | 5.4°C | 3.7°C | 10.6°C | -2.9°C | 173 mm | 86% | 3.7 m/s | 0.9 |
| 1994 | 6.6°C | 5.1°C | 3.5°C | 12.0°C | -2.7°C | 165 mm | 86% | 3.5 m/s | 0.9 |
| 1993 | 7.2°C | 5.7°C | 4.3°C | 12.4°C | 1.1°C | 142 mm | 84% | 3 m/s | 0.7 |
| 1992 | 5.2°C | 3.6°C | 1.9°C | 8.5°C | -6.0°C | 109 mm | 85% | 3.8 m/s | 0.8 |
| 1991 | 7.8°C | 6.2°C | 4.7°C | 11.4°C | 2.1°C | 104 mm | 88% | 3.2 m/s | 0.7 |
| 1990 | 4.2°C | 2.3°C | 0.3°C | 10.3°C | -10.4°C | 152 mm | 85% | 3.6 m/s | 0.7 |
| 1989 | 7.4°C | 6.1°C | 4.8°C | 12.1°C | 1.4°C | 100 mm | 90% | 1.9 m/s | 0.7 |
| 1988 | 6.7°C | 5.5°C | 4.2°C | 10.7°C | 0.4°C | 124 mm | 86% | 2.7 m/s | 0.8 |
| 1987 | 6.2°C | 4.7°C | 3.2°C | 12.4°C | -1.2°C | 143 mm | 83% | 3.4 m/s | 0.8 |
| 1986 | 6.9°C | 5.2°C | 3.6°C | 9.8°C | -0.5°C | 101 mm | 88% | 3.2 m/s | 0.8 |
| 1985 | 5.0°C | 3.5°C | 2.1°C | 7.2°C | -8.7°C | 38 mm | 86% | 2.4 m/s | 0.9 |
| 1984 | 3.8°C | 2.3°C | 0.8°C | 8.2°C | -6.5°C | 140 mm | 84% | 2.8 m/s | 0.8 |
| 1983 ❄️ | 3.3°C | 1.7°C | 0.0°C | 8.0°C | -8.6°C | 106 mm | 83% | 3.3 m/s | — |
| 1982 | 6.6°C | 5.0°C | 3.4°C | 11.3°C | 0.3°C | 175 mm | 85% | 3.1 m/s | — |
| 1981 | 6.9°C | 5.6°C | 4.2°C | 11.9°C | 0.0°C | 190 mm | 85% | 3.5 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 6.5°C with lows near 3.5°C (mean 5°C), based on 45 years of NASA POWER data.
December averages 141 mm of rainfall in Sidney, a relatively wet time of year. The wettest on record was 241 mm in 2025.
The hottest December reached 13.8°C in 2014. The coldest dipped to -10.4°C in 1990.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.7°C. Daytime highs moved from 5.1°C to 6.8°C and overnight lows from 2.1°C to 3.8°C over the same span.
December is one of the cooler months of the year in Sidney and a relatively wet time of year, so plan for around 6.5°C daytime highs and 3.5°C at night.
Yes — December is the coldest month of the year in Sidney, averaging 5°C.
For December in Sidney, pack warm layers and a jacket for chilly mornings, with typical highs of 6.5°C and lows of 3.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 86% — quite humid.
Average wind speed in December is 3.1 m/s. The windiest December on record averaged 3.8 m/s (1992).
The wettest December on record was 2025 with 241 mm. On average, December sees 141 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 Sidney 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.
