December is one of the cooler months of the year in Sarnia, with average highs near 1.2°C and lows around -4.8°C (mean -1.8°C). It is one of the drier months, averaging 57 mm of rainfall and 86% relative humidity across the period.
December is one of the cooler months of the year in Sarnia. Across 45 years of records, the warmest December in Sarnia was 2015 — when the month averaged 3.9°C — while the coldest were 1983 and 1989 at -7.7°C. Typical December days reach 1.2°C with nights near -4.8°C. The long-term trend is warming, about 0.6°C per decade.
December is one of the drier months in Sarnia, averaging 57 mm of rainfall. The wettest December on record was 2016 with 92 mm, while the driest was 1993 at 18 mm.
Relative humidity in Sarnia during December averages 86%. The most humid December was 1986 at 90%, and the least humid was 1988 at 79%.
December receives about 1.2 kWh/m²/day of solar energy in Sarnia. The sunniest December was 2000 at 1.5 kWh/m²/day, and the cloudiest were 2012, 2015 and 2016, among others at 1.1.
Average wind speed in Sarnia during December is 4.4 m/s. The windiest December was 2008 at 5.4 m/s, while the calmest was 1994 at 3.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | -3.4°C | -1.5°C | -2.1°C | -1.2°C | -0.2°C | +3.2°C |
| Avg High | -0.3°C | 1.7°C | 0.7°C | 1.6°C | 2.7°C | +3°C |
| Avg Low | -6.5°C | -4.6°C | -4.9°C | -4.1°C | -3.2°C | +3.3°C |
| Avg Rain | 55 mm | 48 mm | 61 mm | 64 mm | 60 mm | +5 mm |
December temperatures in Sarnia have risen by about 3.1°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -21.9°C (2017) to a record high of 19.7°C (1982).
Rainfall in December is one of the drier months, averaging 57 mm, with a wettest year of 92 mm.
A quieter season to visit Sarnia
If your dates are flexible, the more temperate months of July and August tend to be the most comfortable for visiting Sarnia. That said, December — with days averaging 1.2°C and nights around -4.8°C (mean -1.8°C) and moderate rainfall (57 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 | 0.0°C | -3.4°C | -6.8°C | 9.1°C | -14.3°C | 64 mm | 83% | 4.9 m/s | — |
| 2024 | 2.0°C | -0.6°C | -3.2°C | 10.9°C | -11.1°C | 66 mm | 85% | 4.4 m/s | 1.2 |
| 2023 | 5.5°C | 2.8°C | 0.2°C | 15.3°C | -5.6°C | 51 mm | 87% | 3.4 m/s | 1.2 |
| 2022 | 2.2°C | -0.9°C | -3.9°C | 10.0°C | -15.3°C | 62 mm | 83% | 4.7 m/s | 1.2 |
| 2021 | 4.4°C | 1.1°C | -2.1°C | 15.8°C | -7.2°C | 48 mm | 83% | 4.4 m/s | 1.3 |
| 2020 | 2.3°C | -0.4°C | -3.1°C | 11.0°C | -7.7°C | 67 mm | 85% | 4.5 m/s | 1.2 |
| 2019 | 2.8°C | -0.2°C | -3.2°C | 8.4°C | -11.3°C | 61 mm | 87% | 4.3 m/s | 1.3 |
| 2018 | 2.3°C | -0.3°C | -2.9°C | 9.9°C | -8.5°C | 52 mm | 88% | 3.7 m/s | 1.3 |
| 2017 | -1.5°C | -4.6°C | -7.7°C | 11.0°C | -21.9°C | 62 mm | 86% | 4.2 m/s | 1.3 |
| 2016 🌧️ | -0.1°C | -3.0°C | -6.0°C | 7.3°C | -19.0°C | 92 mm | 89% | 4.9 m/s | 1.1 |
| 2015 🔥 | 7.2°C | 3.9°C | 0.7°C | 15.9°C | -4.1°C | 71 mm | 87% | 4.4 m/s | 1.1 |
| 2014 | 2.1°C | -0.3°C | -2.8°C | 9.4°C | -10.8°C | 57 mm | 84% | 4.1 m/s | 1.2 |
| 2013 | -2.0°C | -4.9°C | -7.8°C | 9.6°C | -18.0°C | 69 mm | 87% | 4.2 m/s | 1.2 |
| 2012 | 4.0°C | 1.0°C | -2.1°C | 14.5°C | -9.1°C | 72 mm | 87% | 4.1 m/s | 1.1 |
| 2011 | 2.9°C | 0.0°C | -2.9°C | 11.6°C | -8.7°C | 65 mm | 87% | 3.9 m/s | 1.3 |
| 2010 | -1.6°C | -3.9°C | -6.3°C | 5.8°C | -14.1°C | 43 mm | 87% | 4.9 m/s | 1.2 |
| 2009 | 0.6°C | -2.1°C | -4.8°C | 8.0°C | -10.6°C | 57 mm | 83% | 4.5 m/s | 1.3 |
| 2008 | -0.4°C | -3.8°C | -7.2°C | 10.3°C | -15.1°C | 77 mm | 87% | 5.4 m/s | 1.2 |
| 2007 | 0.5°C | -2.2°C | -4.9°C | 6.8°C | -9.8°C | 76 mm | 87% | 4.3 m/s | 1.1 |
| 2006 | 4.2°C | 1.2°C | -1.8°C | 10.6°C | -8.9°C | 65 mm | 86% | 4.8 m/s | 1.3 |
| 2005 | -1.4°C | -3.5°C | -5.7°C | 2.7°C | -11.8°C | 53 mm | 88% | 4.3 m/s | 1.2 |
| 2004 | 0.9°C | -2.3°C | -5.4°C | 13.2°C | -16.3°C | 72 mm | 86% | 5.1 m/s | 1.3 |
| 2003 | 1.6°C | -0.8°C | -3.3°C | 5.2°C | -8.7°C | 61 mm | 84% | 4.2 m/s | 1.4 |
| 2002 | 0.6°C | -2.4°C | -5.3°C | 6.8°C | -12.3°C | 35 mm | 84% | 4.5 m/s | 1.3 |
| 2001 | 4.2°C | 1.3°C | -1.6°C | 16.5°C | -8.6°C | 39 mm | 86% | 4.4 m/s | 1.4 |
| 2000 | -3.5°C | -6.4°C | -9.3°C | 1.7°C | -17.7°C | 70 mm | 90% | 4.5 m/s | 1.5 |
| 1999 | 2.3°C | -1.1°C | -4.5°C | 13.7°C | -11.7°C | 69 mm | 82% | 4.6 m/s | 1.2 |
| 1998 | 5.2°C | 1.2°C | -2.7°C | 16.9°C | -12.7°C | 49 mm | 81% | 4.5 m/s | 1.4 |
| 1997 | 1.8°C | -0.8°C | -3.4°C | 5.6°C | -11.3°C | 41 mm | 86% | 4.1 m/s | 1.3 |
| 1996 | 1.2°C | -1.6°C | -4.4°C | 8.3°C | -15.7°C | 65 mm | 89% | 4 m/s | 1.1 |
| 1995 | -1.8°C | -4.9°C | -7.9°C | 4.4°C | -13.3°C | 25 mm | 84% | 4.4 m/s | 1.4 |
| 1994 | 3.4°C | 0.1°C | -3.2°C | 10.3°C | -9.1°C | 47 mm | 88% | 3.3 m/s | 1.1 |
| 1993 | 0.4°C | -2.3°C | -5.1°C | 8.0°C | -14.7°C | 18 mm | 83% | 4.1 m/s | 1.1 |
| 1992 | 1.5°C | -1.4°C | -4.3°C | 6.4°C | -11.7°C | 43 mm | 85% | 4.2 m/s | 1.1 |
| 1991 | 1.4°C | -2.1°C | -5.6°C | 11.0°C | -12.3°C | 43 mm | 86% | 4.3 m/s | 1.3 |
| 1990 | 1.5°C | -1.8°C | -5.1°C | 8.4°C | -15.7°C | 78 mm | 85% | 4.6 m/s | 1.2 |
| 1989 | -4.7°C | -7.7°C | -10.7°C | 2.9°C | -16.4°C | 31 mm | 83% | 4 m/s | 1.3 |
| 1988 | 0.4°C | -2.8°C | -6.1°C | 9.0°C | -13.3°C | 36 mm | 79% | 4.9 m/s | 1.2 |
| 1987 | 1.7°C | -1.1°C | -3.8°C | 9.4°C | -12.6°C | 69 mm | 86% | 4.7 m/s | 1.2 |
| 1986 | 0.3°C | -2.6°C | -5.4°C | 2.6°C | -14.9°C | 54 mm | 90% | 3.7 m/s | 1.2 |
| 1985 | -2.9°C | -6.1°C | -9.4°C | 8.0°C | -17.3°C | 34 mm | 88% | 4.4 m/s | 1.2 |
| 1984 | 2.7°C | -0.9°C | -4.6°C | 12.9°C | -14.2°C | 81 mm | 85% | 4.5 m/s | 1.1 |
| 1983 ❄️ | -4.3°C | -7.7°C | -11.0°C | 2.9°C | -20.6°C | 72 mm | 90% | 4.7 m/s | — |
| 1982 | 4.0°C | 1.0°C | -2.1°C | 19.7°C | -11.6°C | 73 mm | 85% | 4.5 m/s | — |
| 1981 | -0.3°C | -2.9°C | -5.5°C | 6.2°C | -11.5°C | 47 mm | 87% | 4.2 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 1.2°C with lows near -4.8°C (mean -1.8°C), based on 45 years of NASA POWER data.
December averages 57 mm of rainfall in Sarnia, one of the drier months. The wettest on record was 92 mm in 2016.
The hottest December reached 19.7°C in 1982. The coldest dipped to -21.9°C in 2017.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 3.1°C. Daytime highs moved from -0.2°C to 2.8°C and overnight lows from -6.5°C to -3.2°C over the same span.
December is one of the cooler months of the year in Sarnia and one of the drier months, so plan for around 1.2°C daytime highs and -4.8°C at night.
Not quite — December is the 3rd coolest month in Sarnia, averaging -1.8°C.
For December in Sarnia, pack warm layers and a jacket for chilly mornings, with typical highs of 1.2°C and lows of -4.8°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 86% — quite humid.
Average wind speed in December is 4.4 m/s. The windiest December on record averaged 5.4 m/s (2008).
The wettest December on record was 2016 with 92 mm. On average, December sees 57 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 Sarnia 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.
