San Antonio Weather in December
San Antonio, Texas enjoys mild weather during December. Although there can be a few nights of frost, most days are balmy.
This page gives detailed information on the typical December temperature, precipitation, sun, humidity, wind and storms for San Antonio. The numbers here are historical averages based on climate data gathered at the San Antonio International Airport, located a few miles north of the city center.
Temperature
| 65 °F | December average high | 18 °C |
| 42 °F | December average low | 6 °C |
The coldest temperatures overall for the year begin on December 24th and extend into January. On these dates daily highs average 63 degrees Fahrenheit (17 degrees Celsius) while lows are 41 °F (5 °C)
| 23 days | 60 °F max. or more (16 °C) |
| 14 days | 40 °F min. or less (4 °C) |
San Antonio averages 12 days in December when the thermometer reaches into the 70s °F (over 21 °C). Temperatures above 90 °F (32 °C) are not expected here this month.
The thermometer dips to freezing or below on an average of 4 nights.
Rain
| 2.0 in | total precipitation | 51 mm |
| 7 days | of rain |
Half the time, San Antonio receives 0.4 to 2.5 inches (10 to 64 mm) of rainfall in December. One in four years has drier weather, while another one in four is wetter.
Sun
| 48 % | sunshine |
| 10 days | clear skies |
The sun's rays reach the ground in San Antonio during 48 percent of daylight hours on average in December, for a total of 153 hours in the month. Typically on 10 days this month the sky is mainly clear, with at most 30 percent cloud cover.
Sunlight in December at San Antonio averages 10 hours and 17 minutes a day. The shortest days of the year, from around December 16th to 26th, last 10 hours and 16 minutes from sunrise to sunset.
Humidity
| 68 % | December average humidity |
The relative humidity in San Antonio during December usually peaks at 80 percent in the morning then drops to 50 percent by mid afternoon.
| Local Time | 12 am | 3 am | 6 am | 9 am | 12 pm | 3 pm | 6 pm | 9 pm |
| Humidity % | 76 | 79 | 80 | 75 | 57 | 50 | 56 | 70 |
Wind
| 8.4 mph | December wind speed average | 13.5 kph |
December is less windy than most other months in San Antonio.
Storms
| 1 day | rainfall of 0.5 inches (13 mm) or more |
| 1 day | with thunderstorms in December |
Storms of any kind are infrequent during December at San Antonio.
Reference
The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals.