December is one of the cooler months of the year in San Antonio, with average highs near 17.9°C and lows around 5.6°C (mean 11.8°C). It is one of the drier months, averaging 48 mm of rainfall and 71% relative humidity across the period.
December is one of the cooler months of the year in San Antonio. Across 45 years of records, the warmest December in San Antonio was 2021 — when the month averaged 17.8°C — while the coldest was 1989 at 6.1°C. Typical December days reach 17.9°C with nights near 5.6°C. The long-term trend is warming, about 0.8°C per decade.
December is one of the drier months in San Antonio, averaging 48 mm of rainfall. The wettest December on record was 1991 with 312 mm, while the driest was 2004 at 3 mm.
Relative humidity in San Antonio during December averages 71%. The most humid December was 1986 at 84%, and the least humid was 2008 at 55%.
December receives about 2.7 kWh/m²/day of solar energy in San Antonio. The sunniest Decembers were 2010, 2019 and 2020, among others at 3.3 kWh/m²/day, and the cloudiest was 1992 at 1.9.
Average wind speed in San Antonio during December is 2.6 m/s. The windiest Decembers were 2008 and 2011 at 3 m/s, while the calmest was 1994 at 2.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 10.3°C | 11.8°C | 11.0°C | 12.0°C | 14.7°C | +4.4°C |
| Avg High | 16.4°C | 17.8°C | 17.3°C | 18.1°C | 21.2°C | +4.8°C |
| Avg Low | 4.3°C | 5.8°C | 4.7°C | 6.0°C | 8.1°C | +3.8°C |
| Avg Rain | 47 mm | 71 mm | 41 mm | 49 mm | 24 mm | -22 mm |
December temperatures in San Antonio have risen by about 4.7°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -12.8°C (1989) to a record high of 31.4°C (2024).
Rainfall in December is one of the drier months, averaging 48 mm, with a wettest year of 312 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.9°C per decade while lows rose 0.7°C per decade, widening the gap between day and night.
A quieter season to visit San Antonio
If your dates are flexible, the more temperate months of April and October tend to be the most comfortable for visiting San Antonio. That said, December — with days averaging 17.9°C and nights around 5.6°C (mean 11.8°C) and moderate rainfall (48 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 | 21.8°C | 15.1°C | 8.4°C | 29.2°C | 2.2°C | 9 mm | 64% | 2.4 m/s | — |
| 2024 | 21.9°C | 15.7°C | 9.5°C | 31.4°C | 1.3°C | 25 mm | 67% | 2.5 m/s | 2.7 |
| 2023 | 21.0°C | 14.3°C | 7.6°C | 26.0°C | 1.3°C | 23 mm | 67% | 2.4 m/s | 3.1 |
| 2022 | 19.0°C | 12.9°C | 6.8°C | 27.2°C | -8.8°C | 26 mm | 72% | 2.4 m/s | 2.6 |
| 2021 🔥 | 23.8°C | 17.8°C | 11.9°C | 29.0°C | 1.8°C | 16 mm | 76% | 2.3 m/s | 2.7 |
| 2020 | 19.8°C | 12.2°C | 4.5°C | 25.3°C | -1.1°C | 46 mm | 63% | 2.7 m/s | 3.3 |
| 2019 | 20.2°C | 13.1°C | 5.9°C | 27.5°C | -1.0°C | 12 mm | 64% | 2.3 m/s | 3.3 |
| 2018 | 16.8°C | 11.2°C | 5.7°C | 23.0°C | 0.3°C | 73 mm | 73% | 2.9 m/s | 2.9 |
| 2017 | 17.2°C | 11.5°C | 5.8°C | 28.9°C | -2.2°C | 84 mm | 71% | 2.4 m/s | 2.4 |
| 2016 | 17.3°C | 12.1°C | 6.9°C | 26.0°C | -4.9°C | 119 mm | 77% | 2.8 m/s | 2.2 |
| 2015 | 19.3°C | 13.2°C | 7.1°C | 26.5°C | 0.4°C | 44 mm | 77% | 2.5 m/s | 3 |
| 2014 | 17.7°C | 12.7°C | 7.7°C | 24.4°C | -0.9°C | 34 mm | 79% | 2.6 m/s | 2.3 |
| 2013 | 15.5°C | 9.4°C | 3.4°C | 27.6°C | -3.9°C | 15 mm | 73% | 2.3 m/s | 2.7 |
| 2012 | 20.7°C | 14.1°C | 7.4°C | 28.1°C | -2.8°C | 7 mm | 60% | 2.7 m/s | 2.7 |
| 2011 | 16.7°C | 11.1°C | 5.6°C | 24.3°C | -4.8°C | 91 mm | 76% | 3 m/s | 2.3 |
| 2010 | 19.5°C | 12.0°C | 4.6°C | 27.0°C | -3.9°C | 16 mm | 60% | 2.7 m/s | 3.3 |
| 2009 | 13.3°C | 8.0°C | 2.7°C | 20.9°C | -3.8°C | 58 mm | 78% | 2.5 m/s | 2.5 |
| 2008 | 19.2°C | 12.3°C | 5.4°C | 28.1°C | -0.2°C | 10 mm | 55% | 3 m/s | 2.8 |
| 2007 | 20.2°C | 13.2°C | 6.2°C | 28.2°C | -2.9°C | 9 mm | 65% | 2.9 m/s | 3.1 |
| 2006 | 18.6°C | 12.4°C | 6.2°C | 26.0°C | -1.9°C | 60 mm | 65% | 2.7 m/s | 2.6 |
| 2005 | 18.4°C | 11.6°C | 4.9°C | 27.4°C | -2.9°C | 9 mm | 58% | 2.5 m/s | 3 |
| 2004 | 16.3°C | 10.2°C | 4.2°C | 22.3°C | -4.6°C | 3 mm | 75% | 2.4 m/s | 3.1 |
| 2003 | 19.3°C | 12.3°C | 5.2°C | 24.5°C | -0.1°C | 11 mm | 63% | 2.9 m/s | 3.2 |
| 2002 | 16.6°C | 10.7°C | 4.8°C | 22.2°C | -1.6°C | 101 mm | 80% | 2.4 m/s | 2.8 |
| 2001 | 17.5°C | 11.6°C | 5.7°C | 24.6°C | -1.6°C | 94 mm | 76% | 2.6 m/s | 2.7 |
| 2000 | 13.4°C | 7.4°C | 1.5°C | 22.2°C | -2.8°C | 51 mm | 79% | 2.7 m/s | 2.5 |
| 1999 | 19.9°C | 12.5°C | 5.0°C | 28.0°C | -1.7°C | 17 mm | 56% | 2.8 m/s | 3.1 |
| 1998 | 16.6°C | 11.1°C | 5.5°C | 25.4°C | -3.4°C | 30 mm | 78% | 2.8 m/s | 2.6 |
| 1997 | 16.8°C | 10.1°C | 3.3°C | 24.9°C | -4.4°C | 73 mm | 68% | 2.8 m/s | 3.2 |
| 1996 | 18.5°C | 12.0°C | 5.4°C | 27.3°C | -6.6°C | 44 mm | 72% | 2.5 m/s | 2.9 |
| 1995 | 18.6°C | 12.2°C | 5.7°C | 28.2°C | -4.3°C | 35 mm | 70% | 2.5 m/s | 3 |
| 1994 | 18.3°C | 13.0°C | 7.7°C | 26.3°C | 1.4°C | 113 mm | 79% | 2.2 m/s | 2.3 |
| 1993 | 18.0°C | 12.1°C | 6.2°C | 25.4°C | -2.3°C | 22 mm | 68% | 2.7 m/s | 2.5 |
| 1992 | 16.8°C | 11.7°C | 6.5°C | 24.0°C | 0.7°C | 56 mm | 81% | 2.5 m/s | 1.9 |
| 1991 🌧️ | 16.4°C | 12.1°C | 7.7°C | 23.3°C | 0.6°C | 312 mm | 81% | 2.7 m/s | 2.1 |
| 1990 | 17.9°C | 11.4°C | 4.9°C | 26.9°C | -6.6°C | 8 mm | 67% | 2.8 m/s | 3 |
| 1989 ❄️ | 12.8°C | 6.1°C | -0.6°C | 24.2°C | -12.8°C | 9 mm | 64% | 2.8 m/s | 3.1 |
| 1988 | 19.2°C | 12.9°C | 6.6°C | 26.4°C | -0.3°C | 16 mm | 63% | 2.7 m/s | 2.7 |
| 1987 | 18.2°C | 11.9°C | 5.6°C | 29.4°C | -2.3°C | 56 mm | 71% | 2.7 m/s | 2.6 |
| 1986 | 14.2°C | 9.4°C | 4.5°C | 20.8°C | -2.8°C | 158 mm | 84% | 2.3 m/s | 2.2 |
| 1985 | 15.0°C | 8.7°C | 2.4°C | 22.7°C | -6.1°C | 15 mm | 78% | 2.4 m/s | 3.3 |
| 1984 | 20.1°C | 15.1°C | 10.1°C | 24.8°C | -0.9°C | 83 mm | 81% | 2.8 m/s | 2.4 |
| 1983 | 13.2°C | 6.8°C | 0.5°C | 26.0°C | -10.3°C | 12 mm | 64% | 2.9 m/s | — |
| 1982 | 16.2°C | 10.5°C | 4.8°C | 24.3°C | -2.5°C | 52 mm | 73% | 2.9 m/s | — |
| 1981 | 18.3°C | 11.6°C | 4.9°C | 26.1°C | -4.2°C | 17 mm | 68% | 2.6 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 17.9°C with lows near 5.6°C (mean 11.8°C), based on 45 years of NASA POWER data.
December averages 48 mm of rainfall in San Antonio, one of the drier months. The wettest on record was 312 mm in 1991.
The hottest December reached 31.4°C in 2024. The coldest dipped to -12.8°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 4.7°C. Daytime highs moved from 16.6°C to 21.5°C and overnight lows from 4.5°C to 8.8°C over the same span.
December is one of the cooler months of the year in San Antonio and one of the drier months, so plan for around 17.9°C daytime highs and 5.6°C at night.
Not quite — December is the 2nd coolest month in San Antonio, averaging 11.8°C.
For December in San Antonio, pack warm layers and a jacket for chilly mornings, with typical highs of 17.9°C and lows of 5.6°C.
Relative humidity in December averages 71% — moderately humid.
Average wind speed in December is 2.6 m/s. The windiest December on record averaged 3 m/s (2008).
The wettest December on record was 1991 with 312 mm. On average, December sees 48 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 Antonio 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.
