December is one of the cooler months of the year in San Diego, with average highs near 16.9°C and lows around 6.4°C (mean 11.6°C). It is a relatively wet time of year, averaging 53 mm of rainfall and 61% relative humidity across the period.
December is one of the cooler months of the year in San Diego. Across 45 years of records, the warmest December in San Diego was 2025 — when the month averaged 16.1°C — while the coldest was 1987 at 8.8°C. Typical December days reach 16.9°C with nights near 6.4°C. The long-term trend is warming, about 0.6°C per decade.
December is a relatively wet time of year in San Diego, averaging 53 mm of rainfall. The wettest December on record was 2010 with 176 mm, while the driest were 2000 and 2024 at 1 mm.
Relative humidity in San Diego during December averages 61%. The most humid December was 1984 at 72%, and the least humid was 2017 at 34%.
December receives about 2.9 kWh/m²/day of solar energy in San Diego. The sunniest Decembers were 1999, 2006 and 2017 at 3.3 kWh/m²/day, and the cloudiest were 2010 and 2021 at 2.5.
Average wind speed in San Diego during December is 2.3 m/s. The windiest December was 1990 at 3.1 m/s, while the calmest was 2024 at 1.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 11.1°C | 11.0°C | 11.4°C | 12.0°C | 13.6°C | +2.5°C |
| Avg High | 16.4°C | 16.3°C | 16.7°C | 17.1°C | 18.9°C | +2.5°C |
| Avg Low | 5.7°C | 5.6°C | 6.3°C | 6.9°C | 8.3°C | +2.6°C |
| Avg Rain | 58 mm | 39 mm | 50 mm | 71 mm | 41 mm | -17 mm |
December temperatures in San Diego have risen by about 2.6°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -3°C (1990) to a record high of 27.3°C (2025).
Rainfall in December is a relatively wet time of year, averaging 53 mm, with a wettest year of 176 mm.
A quieter season to visit San Diego
If your dates are flexible, the more temperate months of June and September tend to be the most comfortable for visiting San Diego. That said, December — with days averaging 16.9°C and nights around 6.4°C (mean 11.6°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 🔥 | 21.4°C | 16.1°C | 10.7°C | 27.3°C | 5.5°C | 41 mm | 56% | 1.9 m/s | — |
| 2024 | 21.2°C | 15.2°C | 9.1°C | 25.5°C | 6.1°C | 1 mm | 50% | 1.7 m/s | 2.7 |
| 2023 | 19.3°C | 14.0°C | 8.8°C | 24.4°C | 6.8°C | 20 mm | 62% | 1.9 m/s | 3 |
| 2022 | 16.6°C | 11.8°C | 6.9°C | 25.2°C | 2.9°C | 47 mm | 68% | 2 m/s | 2.8 |
| 2021 | 16.4°C | 11.8°C | 7.2°C | 27.0°C | 2.6°C | 116 mm | 69% | 2.4 m/s | 2.5 |
| 2020 | 18.4°C | 12.8°C | 7.2°C | 24.8°C | 3.9°C | 23 mm | 48% | 2.4 m/s | 3 |
| 2019 | 15.3°C | 11.0°C | 6.8°C | 22.2°C | 1.6°C | 109 mm | 70% | 2.3 m/s | 2.7 |
| 2018 | 17.1°C | 12.1°C | 7.2°C | 23.4°C | 1.1°C | 62 mm | 66% | 2.1 m/s | 2.9 |
| 2017 | 21.3°C | 15.0°C | 8.7°C | 26.8°C | 1.5°C | 1 mm | 34% | 2.1 m/s | 3.3 |
| 2016 | 16.7°C | 11.7°C | 6.7°C | 23.1°C | 0.5°C | 129 mm | 68% | 2.6 m/s | 2.8 |
| 2015 | 16.5°C | 11.0°C | 5.5°C | 26.0°C | 0.0°C | 49 mm | 59% | 2.7 m/s | 3.2 |
| 2014 | 17.1°C | 12.7°C | 8.3°C | 25.2°C | 1.0°C | 90 mm | 71% | 1.9 m/s | 2.8 |
| 2013 | 17.4°C | 12.0°C | 6.5°C | 24.9°C | -0.4°C | 15 mm | 54% | 2.3 m/s | 3.1 |
| 2012 | 16.2°C | 11.3°C | 6.5°C | 24.0°C | 1.1°C | 52 mm | 71% | 2.3 m/s | 2.7 |
| 2011 | 15.9°C | 10.4°C | 4.9°C | 23.4°C | 0.2°C | 25 mm | 57% | 2 m/s | 3.2 |
| 2010 🌧️ | 17.1°C | 12.4°C | 7.8°C | 25.1°C | 0.3°C | 176 mm | 70% | 2.5 m/s | 2.5 |
| 2009 | 15.2°C | 10.4°C | 5.7°C | 22.7°C | 0.9°C | 93 mm | 65% | 2.3 m/s | 2.7 |
| 2008 | 15.2°C | 10.5°C | 5.8°C | 25.4°C | -0.3°C | 121 mm | 69% | 2.6 m/s | 2.6 |
| 2007 | 14.9°C | 9.7°C | 4.5°C | 24.2°C | -0.8°C | 41 mm | 64% | 2.5 m/s | 3.1 |
| 2006 | 17.7°C | 11.8°C | 6.0°C | 24.1°C | 2.1°C | 23 mm | 51% | 2.5 m/s | 3.3 |
| 2005 | 18.9°C | 13.3°C | 7.7°C | 25.3°C | 3.5°C | 4 mm | 55% | 1.9 m/s | 2.7 |
| 2004 | 16.3°C | 11.3°C | 6.4°C | 22.3°C | 1.7°C | 96 mm | 67% | 2.5 m/s | 2.9 |
| 2003 | 16.7°C | 11.4°C | 6.1°C | 22.7°C | -0.2°C | 35 mm | 61% | 2.3 m/s | 2.9 |
| 2002 | 16.1°C | 11.3°C | 6.5°C | 21.0°C | 1.7°C | 57 mm | 70% | 2.2 m/s | 3 |
| 2001 | 15.8°C | 10.6°C | 5.5°C | 22.1°C | 1.8°C | 28 mm | 64% | 2.3 m/s | 3.1 |
| 2000 | 19.8°C | 14.1°C | 8.4°C | 24.6°C | 5.4°C | 1 mm | 48% | 2 m/s | 2.9 |
| 1999 | 18.7°C | 12.5°C | 6.3°C | 24.7°C | 2.3°C | 9 mm | 43% | 2.3 m/s | 3.3 |
| 1998 | 16.5°C | 11.0°C | 5.4°C | 24.3°C | -0.7°C | 25 mm | 55% | 2.5 m/s | 3.1 |
| 1997 | 15.6°C | 10.6°C | 5.5°C | 21.2°C | 0.0°C | 61 mm | 61% | 2.7 m/s | 3.1 |
| 1996 | 16.9°C | 11.6°C | 6.4°C | 22.4°C | 2.2°C | 43 mm | 65% | 2.8 m/s | 2.7 |
| 1995 | 18.7°C | 13.1°C | 7.4°C | 25.4°C | 2.6°C | 15 mm | 63% | 1.9 m/s | 2.8 |
| 1994 | 15.6°C | 10.7°C | 5.7°C | 20.3°C | 0.2°C | 28 mm | 65% | 2.2 m/s | 2.8 |
| 1993 | 16.5°C | 10.8°C | 5.2°C | 21.5°C | 1.2°C | 26 mm | 58% | 2.6 m/s | 3.2 |
| 1992 | 14.3°C | 9.3°C | 4.3°C | 18.3°C | -0.7°C | 96 mm | 67% | 2.6 m/s | 2.8 |
| 1991 | 15.6°C | 10.9°C | 6.2°C | 20.7°C | -0.2°C | 59 mm | 64% | 2.4 m/s | 2.7 |
| 1990 | 14.6°C | 9.3°C | 4.0°C | 22.2°C | -3.0°C | 25 mm | 50% | 3.1 m/s | 3 |
| 1989 | 18.8°C | 12.8°C | 6.8°C | 26.9°C | 1.6°C | 7 mm | 45% | 2.4 m/s | 3 |
| 1988 | 15.8°C | 10.4°C | 4.9°C | 25.4°C | -1.7°C | 61 mm | 59% | 2.6 m/s | 3 |
| 1987 ❄️ | 13.9°C | 8.8°C | 3.7°C | 25.1°C | -2.7°C | 51 mm | 67% | 2.3 m/s | 2.8 |
| 1986 | 17.1°C | 11.6°C | 6.1°C | 24.0°C | 2.0°C | 27 mm | 57% | 2 m/s | 2.9 |
| 1985 | 16.6°C | 11.2°C | 5.8°C | 21.1°C | -0.7°C | 38 mm | 64% | 2 m/s | 2.8 |
| 1984 | 14.6°C | 9.7°C | 4.8°C | 18.5°C | 0.2°C | 140 mm | 72% | 2.3 m/s | 2.8 |
| 1983 | 16.1°C | 11.5°C | 6.8°C | 22.1°C | 1.6°C | 86 mm | 71% | 2.6 m/s | — |
| 1982 | 15.5°C | 10.3°C | 5.2°C | 21.2°C | -0.6°C | 83 mm | 65% | 2.7 m/s | — |
| 1981 | 19.0°C | 13.3°C | 7.6°C | 23.9°C | 2.2°C | 28 mm | 57% | 2.2 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 16.9°C with lows near 6.4°C (mean 11.6°C), based on 45 years of NASA POWER data.
December averages 53 mm of rainfall in San Diego, a relatively wet time of year. The wettest on record was 176 mm in 2010.
The hottest December reached 27.3°C in 2025. The coldest dipped to -3°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 16.4°C to 19°C and overnight lows from 6°C to 8.5°C over the same span.
December is one of the cooler months of the year in San Diego and a relatively wet time of year, so plan for around 16.9°C daytime highs and 6.4°C at night.
Not quite — December is the 2nd coolest month in San Diego, averaging 11.6°C.
For December in San Diego, pack warm layers and a jacket for chilly mornings, with typical highs of 16.9°C and lows of 6.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 61% — moderately humid.
Average wind speed in December is 2.3 m/s. The windiest December on record averaged 3.1 m/s (1990).
The wettest December on record was 2010 with 176 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 San Diego 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.
