December is one of the cooler months of the year in Oceanside, with average highs near 17.5°C and lows around 12.8°C (mean 15.2°C). It is a relatively wet time of year, averaging 53 mm of rainfall and 68% relative humidity across the period.
December is one of the cooler months of the year in Oceanside. Across 45 years of records, the warmest Decembers in Oceanside were 2017 and 2025 — when the month averaged 17.7°C — while the coldest was 1987 at 13.4°C. Typical December days reach 17.5°C with nights near 12.8°C. The long-term trend is warming, about 0.3°C per decade.
December is a relatively wet time of year in Oceanside, averaging 53 mm of rainfall. The wettest December on record was 2010 with 190 mm, while the driest was 2000 at 1 mm.
Relative humidity in Oceanside during December averages 68%. The most humid December was 2010 at 78%, and the least humid was 1990 at 55%.
December receives about 2.9 kWh/m²/day of solar energy in Oceanside. The sunniest December was 2017 at 3.3 kWh/m²/day, and the cloudiest was 2010 at 2.5.
Average wind speed in Oceanside during December is 2.7 m/s. The windiest December was 1997 at 3.7 m/s, while the calmest were 2000 and 2005 at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.9°C | 14.9°C | 14.9°C | 15.5°C | 16.0°C | +1.1°C |
| Avg High | 17.4°C | 17.4°C | 17.1°C | 17.6°C | 18.2°C | +0.8°C |
| Avg Low | 12.4°C | 12.4°C | 12.6°C | 13.3°C | 13.8°C | +1.4°C |
| Avg Rain | 54 mm | 36 mm | 45 mm | 79 mm | 48 mm | -6 mm |
December temperatures in Oceanside have risen by about 1°C between 1981–1985 and 2021–2025.
December has ranged from a record low of 5.1°C (1990) to a record high of 24.9°C (2017).
Rainfall in December is a relatively wet time of year, averaging 53 mm, with a wettest year of 190 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.2°C per decade while lows rose 0.4°C per decade, narrowing the gap between day and night.
A quieter season to visit Oceanside
If your dates are flexible, the more temperate months of August and September tend to be the most comfortable for visiting Oceanside. That said, December — with days averaging 17.5°C and nights around 12.8°C (mean 15.2°C) and moderate rainfall (53 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 | 20.0°C | 17.7°C | 15.4°C | 23.9°C | 12.8°C | 49 mm | 74% | 2.2 m/s | — |
| 2024 | 18.2°C | 15.8°C | 13.5°C | 22.2°C | 11.8°C | 2 mm | 75% | 2 m/s | 2.9 |
| 2023 | 19.0°C | 16.8°C | 14.6°C | 22.9°C | 12.8°C | 33 mm | 74% | 2.2 m/s | 2.9 |
| 2022 | 16.8°C | 14.8°C | 12.8°C | 22.1°C | 10.4°C | 53 mm | 75% | 2.2 m/s | 2.7 |
| 2021 | 16.4°C | 14.5°C | 12.6°C | 23.3°C | 10.3°C | 128 mm | 77% | 3 m/s | 2.6 |
| 2020 | 18.6°C | 16.1°C | 13.6°C | 22.5°C | 11.0°C | 22 mm | 65% | 2.4 m/s | 3.1 |
| 2019 | 16.9°C | 15.1°C | 13.3°C | 19.7°C | 10.6°C | 160 mm | 74% | 2.8 m/s | 2.6 |
| 2018 | 17.9°C | 15.8°C | 13.8°C | 21.2°C | 10.6°C | 84 mm | 73% | 2.7 m/s | 3 |
| 2017 🔥 | 20.5°C | 17.7°C | 15.0°C | 24.9°C | 11.3°C | 1 mm | 57% | 2 m/s | 3.3 |
| 2016 | 17.1°C | 15.1°C | 13.0°C | 21.4°C | 10.2°C | 140 mm | 73% | 2.9 m/s | 2.7 |
| 2015 | 17.8°C | 15.6°C | 13.3°C | 24.4°C | 9.8°C | 37 mm | 62% | 3.4 m/s | 3.1 |
| 2014 | 18.3°C | 16.4°C | 14.5°C | 23.6°C | 8.6°C | 91 mm | 73% | 2.8 m/s | 2.7 |
| 2013 | 18.0°C | 15.5°C | 13.0°C | 22.4°C | 9.2°C | 11 mm | 64% | 2 m/s | 3.2 |
| 2012 | 16.4°C | 14.5°C | 12.6°C | 20.4°C | 9.4°C | 52 mm | 75% | 2.8 m/s | 2.7 |
| 2011 | 16.8°C | 14.4°C | 12.0°C | 20.3°C | 10.2°C | 19 mm | 64% | 2.1 m/s | 3.2 |
| 2010 🌧️ | 16.6°C | 14.5°C | 12.5°C | 23.8°C | 8.7°C | 190 mm | 78% | 3 m/s | 2.5 |
| 2009 | 16.3°C | 14.3°C | 12.2°C | 21.2°C | 9.4°C | 75 mm | 71% | 2.7 m/s | 2.8 |
| 2008 | 16.3°C | 14.2°C | 12.1°C | 22.1°C | 8.7°C | 102 mm | 72% | 2.9 m/s | 2.7 |
| 2007 | 16.3°C | 13.9°C | 11.6°C | 21.5°C | 8.1°C | 39 mm | 67% | 2.9 m/s | 3.1 |
| 2006 | 18.1°C | 15.5°C | 12.8°C | 22.4°C | 10.2°C | 22 mm | 61% | 2.8 m/s | 3.2 |
| 2005 | 17.9°C | 15.6°C | 13.3°C | 22.0°C | 11.0°C | 7 mm | 70% | 1.9 m/s | 2.8 |
| 2004 | 17.7°C | 15.4°C | 13.0°C | 22.7°C | 10.7°C | 96 mm | 69% | 2.8 m/s | 2.9 |
| 2003 | 17.1°C | 14.9°C | 12.6°C | 20.8°C | 9.2°C | 28 mm | 69% | 2.9 m/s | 2.8 |
| 2002 | 16.8°C | 14.8°C | 12.8°C | 19.7°C | 10.1°C | 49 mm | 74% | 2.9 m/s | 3 |
| 2001 | 16.3°C | 14.3°C | 12.2°C | 21.9°C | 10.5°C | 25 mm | 70% | 2.8 m/s | 2.9 |
| 2000 | 18.5°C | 16.1°C | 13.6°C | 22.0°C | 11.7°C | 1 mm | 67% | 1.9 m/s | 3 |
| 1999 | 18.4°C | 15.6°C | 12.8°C | 22.0°C | 10.6°C | 10 mm | 60% | 2.2 m/s | 3.2 |
| 1998 | 17.0°C | 14.4°C | 11.8°C | 24.4°C | 7.7°C | 21 mm | 62% | 2.8 m/s | 3 |
| 1997 | 18.1°C | 15.6°C | 13.1°C | 23.0°C | 9.2°C | 55 mm | 62% | 3.7 m/s | 3.1 |
| 1996 | 17.4°C | 15.0°C | 12.6°C | 21.3°C | 10.0°C | 52 mm | 73% | 3.1 m/s | 2.7 |
| 1995 | 18.1°C | 15.8°C | 13.5°C | 21.8°C | 11.4°C | 19 mm | 74% | 2.7 m/s | 2.8 |
| 1994 | 16.6°C | 14.3°C | 12.0°C | 21.2°C | 9.5°C | 22 mm | 70% | 2.7 m/s | 2.8 |
| 1993 | 17.8°C | 15.1°C | 12.4°C | 22.3°C | 8.7°C | 22 mm | 64% | 2.9 m/s | 3.1 |
| 1992 | 16.4°C | 14.1°C | 11.8°C | 20.6°C | 8.8°C | 87 mm | 66% | 3.4 m/s | 2.8 |
| 1991 | 17.2°C | 14.9°C | 12.6°C | 21.0°C | 9.2°C | 52 mm | 69% | 2.8 m/s | 2.8 |
| 1990 | 17.0°C | 14.2°C | 11.5°C | 23.5°C | 5.1°C | 15 mm | 55% | 3.6 m/s | 3.1 |
| 1989 | 19.6°C | 16.6°C | 13.6°C | 24.2°C | 10.9°C | 6 mm | 58% | 2.4 m/s | 3.1 |
| 1988 | 16.4°C | 14.0°C | 11.6°C | 22.9°C | 7.0°C | 65 mm | 64% | 3.1 m/s | 2.8 |
| 1987 ❄️ | 15.6°C | 13.4°C | 11.1°C | 21.3°C | 5.3°C | 65 mm | 66% | 3.5 m/s | 2.7 |
| 1986 | 18.5°C | 15.9°C | 13.4°C | 21.5°C | 11.3°C | 25 mm | 63% | 2.5 m/s | 2.8 |
| 1985 | 17.8°C | 15.1°C | 12.4°C | 21.4°C | 7.7°C | 32 mm | 68% | 2.3 m/s | 2.9 |
| 1984 | 16.0°C | 13.8°C | 11.5°C | 19.3°C | 9.0°C | 135 mm | 71% | 3.2 m/s | 2.7 |
| 1983 | 17.1°C | 15.0°C | 12.9°C | 21.0°C | 10.5°C | 78 mm | 73% | 3.1 m/s | — |
| 1982 | 17.2°C | 14.6°C | 12.1°C | 21.1°C | 8.2°C | 52 mm | 66% | 3.5 m/s | — |
| 1981 | 18.6°C | 15.9°C | 13.3°C | 23.1°C | 10.8°C | 28 mm | 67% | 2.6 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 17.5°C with lows near 12.8°C (mean 15.2°C), based on 45 years of NASA POWER data.
December averages 53 mm of rainfall in Oceanside, a relatively wet time of year. The wettest on record was 190 mm in 2010.
The hottest December reached 24.9°C in 2017. The coldest dipped to 5.1°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°C. Daytime highs moved from 17.3°C to 18.1°C and overnight lows from 12.4°C to 13.8°C over the same span.
December is one of the cooler months of the year in Oceanside and a relatively wet time of year, so plan for around 17.5°C daytime highs and 12.8°C at night.
Not quite — December is the 4th coolest month in Oceanside, averaging 15.2°C.
For December in Oceanside, pack light layers you can adjust through the day, with typical highs of 17.5°C and lows of 12.8°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 68% — moderately humid.
Average wind speed in December is 2.7 m/s. The windiest December on record averaged 3.7 m/s (1997).
The wettest December on record was 2010 with 190 mm. On average, December sees 53 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 Oceanside 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.
