December is one of the cooler months of the year in Olympia, with average highs near 6.1°C and lows around 1°C (mean 3.6°C). It is a relatively wet time of year, averaging 260 mm of rainfall and 95% relative humidity across the period.
December is one of the cooler months of the year in Olympia. Across 45 years of records, the warmest December in Olympia was 2023 — when the month averaged 6.7°C — while the coldest was 1983 at 0°C. Typical December days reach 6.1°C with nights near 1°C. The long-term trend is warming, about 0.4°C per decade.
December is a relatively wet time of year in Olympia, averaging 260 mm of rainfall. The wettest December on record was 2015 with 487 mm, while the driest was 1985 at 79 mm.
Relative humidity in Olympia during December averages 95%. The most humid Decembers were 2012 and 2019 at 98%, and the least humid was 1990 at 88%.
December receives about 0.9 kWh/m²/day of solar energy in Olympia. The sunniest Decembers were 1985 and 2009 at 1.1 kWh/m²/day, and the cloudiest were 2012, 2015 and 2019, among others at 0.7.
Average wind speed in Olympia during December is 0.2 m/s. The windiest Decembers were 2009, 2011 and 2013, among others at 0.3 m/s, while the calmest were 2023, 2024 and 2025, among others at 0.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 2.8°C | 3.5°C | 3.6°C | 3.7°C | 4.7°C | +1.9°C |
| Avg High | 5.7°C | 6.0°C | 6.2°C | 6.1°C | 7.0°C | +1.3°C |
| Avg Low | -0.1°C | 1.0°C | 1.0°C | 1.3°C | 2.4°C | +2.5°C |
| Avg Rain | 215 mm | 289 mm | 242 mm | 256 mm | 320 mm | +105 mm |
December temperatures in Olympia have risen by about 2.6°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -15.8°C (1990) to a record high of 14°C (2014).
Rainfall in December is a relatively wet time of year, averaging 260 mm, with a wettest year of 487 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.3°C per decade while lows rose 0.5°C per decade, narrowing the gap between day and night.
A quieter season to visit Olympia
If your dates are flexible, the more temperate months of August and July tend to be the most comfortable for visiting Olympia. That said, December — with days averaging 6.1°C and nights around 1°C (mean 3.6°C) and higher rainfall (260 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 | 8.3°C | 6.2°C | 4.1°C | 14.0°C | -0.1°C | 427 mm | 98% | 0.2 m/s | — |
| 2024 | 7.6°C | 5.3°C | 3.0°C | 10.8°C | -1.5°C | 336 mm | 97% | 0.2 m/s | 0.9 |
| 2023 🔥 | 9.1°C | 6.7°C | 4.2°C | 14.0°C | -0.5°C | 316 mm | 96% | 0.2 m/s | 0.8 |
| 2022 | 5.0°C | 2.6°C | 0.2°C | 12.2°C | -7.0°C | 296 mm | 96% | 0.2 m/s | 0.8 |
| 2021 | 4.1°C | 2.2°C | 0.2°C | 12.5°C | -10.3°C | 283 mm | 97% | 0.2 m/s | 0.8 |
| 2020 | 8.1°C | 5.4°C | 2.7°C | 12.7°C | -1.6°C | 264 mm | 94% | 0.2 m/s | 0.9 |
| 2019 | 6.9°C | 4.9°C | 2.9°C | 11.1°C | -0.6°C | 266 mm | 98% | 0.2 m/s | 0.7 |
| 2018 | 7.2°C | 4.8°C | 2.3°C | 11.6°C | -3.6°C | 291 mm | 95% | 0.2 m/s | 0.9 |
| 2017 | 6.2°C | 3.2°C | 0.3°C | 10.6°C | -3.9°C | 189 mm | 95% | 0.2 m/s | 1 |
| 2016 | 3.4°C | 1.3°C | -0.9°C | 8.0°C | -7.0°C | 198 mm | 94% | 0.2 m/s | 0.9 |
| 2015 🌧️ | 6.5°C | 4.5°C | 2.5°C | 13.8°C | -3.9°C | 487 mm | 96% | 0.2 m/s | 0.7 |
| 2014 | 8.2°C | 5.5°C | 2.8°C | 14.0°C | -5.1°C | 251 mm | 93% | 0.2 m/s | 1 |
| 2013 | 4.2°C | 1.5°C | -1.1°C | 10.4°C | -10.4°C | 90 mm | 90% | 0.3 m/s | 0.9 |
| 2012 | 5.5°C | 3.7°C | 1.8°C | 10.0°C | -2.5°C | 333 mm | 98% | 0.2 m/s | 0.7 |
| 2011 | 6.0°C | 3.1°C | 0.2°C | 10.8°C | -3.8°C | 128 mm | 94% | 0.3 m/s | 1 |
| 2010 | 6.8°C | 4.5°C | 2.3°C | 12.1°C | -4.7°C | 325 mm | 94% | 0.2 m/s | 0.8 |
| 2009 | 5.0°C | 1.8°C | -1.4°C | 10.6°C | -10.4°C | 135 mm | 88% | 0.3 m/s | 1.1 |
| 2008 | 3.7°C | 1.3°C | -1.2°C | 10.7°C | -9.7°C | 185 mm | 94% | 0.2 m/s | 0.8 |
| 2007 | 5.1°C | 3.0°C | 0.8°C | 13.7°C | -4.1°C | 375 mm | 97% | 0.2 m/s | 0.7 |
| 2006 | 6.1°C | 3.6°C | 1.1°C | 11.8°C | -3.0°C | 275 mm | 95% | 0.2 m/s | 0.8 |
| 2005 | 6.4°C | 3.9°C | 1.3°C | 13.4°C | -4.4°C | 301 mm | 94% | 0.2 m/s | 0.9 |
| 2004 | 7.9°C | 5.2°C | 2.6°C | 12.9°C | -0.5°C | 181 mm | 95% | 0.2 m/s | 0.8 |
| 2003 | 6.6°C | 4.5°C | 2.4°C | 11.6°C | -4.4°C | 224 mm | 96% | 0.2 m/s | 0.8 |
| 2002 | 7.8°C | 5.1°C | 2.5°C | 13.9°C | -1.8°C | 310 mm | 96% | 0.2 m/s | 0.7 |
| 2001 | 6.4°C | 3.8°C | 1.2°C | 10.9°C | -2.8°C | 318 mm | 95% | 0.2 m/s | 0.9 |
| 2000 | 6.6°C | 3.8°C | 1.1°C | 10.7°C | -4.6°C | 118 mm | 94% | 0.2 m/s | 0.9 |
| 1999 | 7.6°C | 5.1°C | 2.6°C | 11.3°C | -1.5°C | 285 mm | 97% | 0.2 m/s | 0.8 |
| 1998 | 5.5°C | 3.1°C | 0.7°C | 12.6°C | -10.3°C | 420 mm | 93% | 0.2 m/s | 0.8 |
| 1997 | 6.8°C | 4.2°C | 1.6°C | 11.7°C | -2.4°C | 174 mm | 95% | 0.2 m/s | 1 |
| 1996 | 5.8°C | 3.3°C | 0.8°C | 13.8°C | -3.7°C | 462 mm | 97% | 0.2 m/s | 0.8 |
| 1995 | 6.8°C | 4.3°C | 1.7°C | 12.1°C | -4.4°C | 308 mm | 95% | 0.2 m/s | 0.8 |
| 1994 | 6.0°C | 3.6°C | 1.2°C | 12.0°C | -6.1°C | 389 mm | 95% | 0.2 m/s | 0.9 |
| 1993 | 7.2°C | 4.2°C | 1.2°C | 13.1°C | -3.6°C | 273 mm | 93% | 0.3 m/s | 0.8 |
| 1992 | 4.4°C | 2.1°C | -0.2°C | 8.2°C | -5.2°C | 184 mm | 94% | 0.2 m/s | 0.9 |
| 1991 | 7.1°C | 4.8°C | 2.4°C | 11.4°C | -2.8°C | 182 mm | 96% | 0.2 m/s | 0.9 |
| 1990 | 3.1°C | 0.3°C | -2.5°C | 9.9°C | -15.8°C | 209 mm | 88% | 0.2 m/s | 0.8 |
| 1989 | 8.0°C | 5.0°C | 1.9°C | 13.5°C | -2.3°C | 179 mm | 95% | 0.3 m/s | 0.9 |
| 1988 | 6.6°C | 3.7°C | 0.8°C | 12.1°C | -4.3°C | 185 mm | 95% | 0.2 m/s | 0.8 |
| 1987 | 5.2°C | 2.5°C | -0.2°C | 12.5°C | -4.6°C | 283 mm | 94% | 0.2 m/s | 0.8 |
| 1986 | 6.9°C | 3.9°C | 1.0°C | 9.5°C | -3.5°C | 202 mm | 95% | 0.2 m/s | 0.8 |
| 1985 | 5.3°C | 1.8°C | -1.7°C | 8.7°C | -15.5°C | 79 mm | 92% | 0.3 m/s | 1.1 |
| 1984 | 3.8°C | 1.1°C | -1.6°C | 6.7°C | -7.7°C | 176 mm | 94% | 0.2 m/s | 1 |
| 1983 ❄️ | 2.8°C | 0.0°C | -2.8°C | 8.5°C | -14.4°C | 206 mm | 90% | 0.2 m/s | — |
| 1982 | 5.8°C | 3.2°C | 0.5°C | 12.6°C | -4.9°C | 315 mm | 95% | 0.2 m/s | — |
| 1981 | 6.6°C | 3.9°C | 1.3°C | 11.4°C | -3.4°C | 309 mm | 97% | 0.2 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 6.1°C with lows near 1°C (mean 3.6°C), based on 45 years of NASA POWER data.
December averages 260 mm of rainfall in Olympia, a relatively wet time of year. The wettest on record was 487 mm in 2015.
The hottest December reached 14°C in 2014. The coldest dipped to -15.8°C in 1990.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 2.6°C. Daytime highs moved from 4.9°C to 6.8°C and overnight lows from -0.9°C to 2.3°C over the same span.
December is one of the cooler months of the year in Olympia and a relatively wet time of year, so plan for around 6.1°C daytime highs and 1°C at night.
Yes — December is the coldest month of the year in Olympia, averaging 3.6°C.
For December in Olympia, pack warm layers and a jacket for chilly mornings, with typical highs of 6.1°C and lows of 1°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 95% — quite humid.
Average wind speed in December is 0.2 m/s. The windiest December on record averaged 0.3 m/s (1985).
The wettest December on record was 2015 with 487 mm. On average, December sees 260 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 Olympia 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.
