WEATHER · CLIMATE NORMALS · 1991–2020
San Antonio Climate — Averages by Month
What the weather in San Antonio, USaverages across a standard 30-year period. Each month's figure is the 1991–2020 mean temperature and total rainfall from the ERA5 reanalysis — the long-run normal a place settles around, not a forecast for any particular day.
Month-by-month normals
| Month | Avg temperature | Avg rainfall |
|---|---|---|
| January | 11.0 °C · coldest | 60.3 mm |
| February | 13.3 °C | 62.0 mm |
| March | 16.9 °C | 83.7 mm |
| April | 20.6 °C | 83.1 mm |
| May | 24.4 °C | 109.1 mm · wettest |
| June | 27.6 °C | 76.0 mm |
| July | 28.7 °C | 53.8 mm |
| August | 29.1 °C · warmest | 52.8 mm |
| September | 26.2 °C | 81.6 mm |
| October | 21.5 °C | 86.2 mm |
| November | 15.8 °C | 71.2 mm |
| December | 11.8 °C | 66.7 mm |
How to read these numbers
These are reanalysis normals, not readings from a single weather station. They come from the ERA5 0.25° (~25 km) global reanalysis grid, sampled at the grid cell nearest San Antonio — centred at 29.50°N, 98.50°W. A reanalysis blends observations with a physics model onto an even grid, so a coastal or mountain city's cell can read a little cooler, warmer, wetter or drier than the city centre itself. The month-to-month shape — when it's hot, when it rains — is what these normals capture best.
“Normal” means the 1991–2020 average, the current World Meteorological Organization standard period. A normal is what a place tends toward over decades — any single day, month or year can and will depart from it.