San Antonio recorded its first triple-digit temperature of 2026. Five weather warnings and 33 advisories were in effect for 33 regions in the area.

The heat arrived as the city continued to manage rising summer temperatures. Climate data analysis indicates that San Antonio's average number of 100-degree days increased from 14 per year between 1990 and 2010 to 29 per year over the past 15 years. Public health officials noted earlier heat impacts, with Metro Health reporting 94 heat-related illnesses from May 1 to June 13, 2026. Most of those cases involved heat exhaustion among vulnerable populations.

Shelby Ebertowski, a meteorologist, identified moisture as a primary driver of the intense conditions. "The humidity is the big factor, especially when you get, let’s say, Tropical Storm Bertha, or you just get a little bit more of that Gulf moisture making its way to Texas, it’s going to be feeling even warmer," she said. Ebertowski added that high moisture levels increase physical strain. "It takes more of a toll on your body on days, (where we) see the high humidity," she said.

Dr. Anna Garza, an emergency medicine physician with Baptist Health System, explained the biological mechanics of heat stress. "The issue is that because it’s so humid, the moisture on our skin just can’t evaporate, which prevents our body’s natural cooling," Garza said. She added that this failure to cool forces the cardiovascular system to compensate.

"It can make our heart work really hard," she said. Garza also issued specific warnings regarding child safety in vehicles. "People don’t realize is that the metal portion of that buckle can get up to greater than 150 degrees Fahrenheit, and that can cause second degree burns, especially in children," she said.