San Antonio weather in December
In December, San Antonio has an average high of 18 °C64 °F and an average low of 5 °C42 °F, with about 45 mm1.8 in of precipitation. It is the 11th warmest month of the year and ranks 11th for precipitation.
How December compares with other months
Compared with November, December is 4.6 °C8.3 °F cooler on average. Compared with January, December is 1 °C1.7 °F warmer on average. Daylight lasts about 10.3 hours around the middle of the month. Average relative humidity is 69% and the average cloud amount 55%.
Is December a good time to visit San Antonio?
Yes — December is one of the most comfortable months to visit San Antonio by our comfort score, which favours average highs of 21–28 °C, lows above 5 °C, little rain and moderate humidity.
What to wear in December
For San Antonio in December, pack light layers — T-shirts plus a light sweater or jacket and an extra layer for the cooler mornings and evenings.
December in nearby places
| Place | High °C°F | Low °C°F | Precip. mmin |
|---|---|---|---|
| San Antonio | 1864 | 542 | 451.8 |
| Austin | 1762 | 440 | 491.9 |
| Killeen | 1660 | 338 | 461.8 |
| Corpus Christi | 2169 | 1050 | 371.5 |
| Piedras Negras | 2068 | 643 | 180.7 |
| Ciudad Acuña | 1967 | 542 | 170.7 |
| Nuevo Laredo | 2169 | 846 | 281.1 |
| College Station | 1661 | 541 | 833.3 |
| Waco | 1560 | 338 | 652.6 |
Nearby places that are more than 1 °C1.8 °F warmer in December: Corpus Christi, Piedras Negras and Nuevo Laredo; cooler: Austin, Killeen, College Station and Waco.
Other months in San Antonio
- January17 °C63 °F / 5 °C40 °F
- February20 °C68 °F / 6 °C44 °F
- March24 °C76 °F / 11 °C51 °F
- April29 °C84 °F / 15 °C59 °F
- May32 °C89 °F / 19 °C67 °F
- June35 °C95 °F / 23 °C73 °F
- July36 °C96 °F / 24 °C75 °F
- August36 °C97 °F / 24 °C76 °F
- September32 °C90 °F / 21 °C70 °F
- October28 °C83 °F / 16 °C60 °F
- November23 °C73 °F / 10 °C50 °F
- December18 °C64 °F / 5 °C42 °F
Frequently asked questions
How warm is San Antonio in December?
In December the average high in San Antonio is 18 °C (64 °F) and the average low is 5 °C (42 °F).
Does it rain a lot in San Antonio in December?
On average about 45 mm (1.8 in) of precipitation falls in December; it ranks 11th of the 12 months.
Is December the warmest month in San Antonio?
No. The warmest month in San Antonio is August, with an average high of 36 °C (97 °F). The coldest month is January, with an average low of 5 °C (40 °F).
How long is the day in San Antonio in December?
In the middle of December the day in San Antonio lasts about 10.3 hours from sunrise to sunset. The value is calculated from the position of the city and the sun.
How humid is San Antonio in December?
The average relative humidity in December is about 69%. This is a long-term average for the whole day.
How cloudy is San Antonio in December?
On average about 55% of the sky is covered by cloud in December. This is the mean cloud amount from satellite data, not the number of sunny days.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.
The grid cell’s average elevation is 302 m, while San Antonio lies at about 198 m. Temperatures on this page were therefore adjusted by +0.7 °C1.2 °F using the standard lapse rate of 6.5 °C per 1,000 m.