| Flash flood | San Antonio sits at the southern end of so-called "Flash Flood Alley," a crescent-shaped strip that runs from near Dallas toward San Antonio and then west through the Hill Country. Steep slopes, thin soils, and shallow creeks make water rise in minutes. Bexar County warns that drivers can be trapped or swept away "in seconds and without warning." More than half of Texas flood deaths over the last six decades happened in vehicles. In July 2025, the Guadalupe River rose more than 20 feet (6 m) in a few hours in Kerr County, about 70 miles (113 km) from the city, with dozens killed. | Ch. 10 |
| Extreme heat | Long, hot summers; the National Weather Service considers heat the leading cause of weather-related deaths in the US. A summer blackout turns a closed-up apartment into a serious risk for older adults, the sick, and pets. | Ch. 10 |
| Winter storms and power grid failures | In February 2021, Winter Storm Uri forced ERCOT, the grid operator for most of Texas, to order rolling outages; millions of people went days without power. The state counted 246 deaths, most from hypothermia, and at least 19 from carbon monoxide while trying to keep warm. SAWS issued a boil water notice for the whole city. | Ch. 10 and 14 |
| Tornadoes and severe storms | Hail, strong winds, and tornadoes occur in the region, especially in spring. On a first floor, take shelter in an interior room with no windows. | Ch. 10 |
| Hurricane remnants and tropical storms | The city is inland, but tropical systems that hit the coast can bring torrential rain and flooding days later. San Antonio also receives evacuees from the coast: stores and gas stations run empty. | Ch. 10 |
| Drought | Long dry periods and staged watering restrictions from SAWS; they raise the risk of fires and lower the quality of soil and creeks. | Ch. 3 |
| Grass and brush fires | With drought, wind, and dry grass, fires spread fast across vacant lots and the edges of the city. Smoke affects air quality. | Ch. 10 |
