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San Antonio sits at the southern edge of the Texas Hill Country, on the Balcones Escarpment in south-central Texas at approximately 29.42°N, 98.49°W. It has a humid subtropical climate bordering semi-arid (Köppen Cfa) — with long, very hot summers and mild winters — and a marked risk of both drought and flash flooding.
Summer, from June to September, is long and very hot, with July and August the hottest — average highs around 35–36°C, with prolonged heatwaves above 38°C — and the humidity off the Gulf makes it oppressive. Rain is scarce in midsummer, and the region is prone to prolonged drought when the Gulf moisture fails to arrive.
Winter, from December to February, is mild and short, with January the coolest month — average highs around 18°C and lows near 5°C. Frost occurs on the coldest nights, snow is very rare, and the season is generally sunny and pleasant, though occasional Arctic outbreaks can bring brief, sharp freezes.
San Antonio receives around 800–850 mm of rain a year, with spring and autumn maxima and a dry midsummer; the rain often arrives in torrential bursts, and the escarpment makes the region among the most flash-flood-prone in the country. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.
San Antonio sits in Flash Flood Alley, where the Balcones Escarpment lifts moist Gulf air into stationary, torrential storms and the thin Hill Country soils shed the water almost instantly into the rivers — the region has recorded some of the most extreme rainfall rates ever measured in the United States.
To follow any single measurement in San Antonio more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.