SAN ANTONIO — Climate Central found that San Antonio’s average fall temperature has increased by 3.8 degrees since 1970. The organization reported that this increase aligns with a 21-day extension of above-average temperatures. Climate Central's attribution science indicates that the 3.8-degree temperature rise in San Antonio's fall is associated with a 4 on a scale where 4 means the event would have been rare without climate change.

Fall is the third fastest-warming season in San Antonio, according to meteorologist Shel Winkley of Climate Central. "Three-point-eight degrees may not sound like a lot," Winkley said. "So as long as we can all understand that this is not the same kind of fall weather that we’ve experienced and there’s something that we can do about it, then we can call it whatever we need to," he said.

Timeline

On September 27, 2026, San Antonio is experiencing its hottest September on record. High temperatures in San Antonio are forecast to reach the mid-90s on September 27, 2026. There is a 20 percent chance of rain in San Antonio on the afternoon of September 27, 2026.

A disturbance moving from the northwest is expected to cause storms in the Hill Country on the afternoon of September 27, 2026. There is a 20 percent chance of rain in the Hill Country late on Sunday, September 27, 2026. Storms may reach San Antonio by the evening of September 27, 2026. A storm system is forecast to approach Texas by midweek, pulling moisture into the region and increasing the chance of rain.

Temperatures in San Antonio are forecast to remain in the mid to upper 90s through at least Monday, September 28, 2026. Rain is forecast for San Antonio on Wednesday and Thursday of the week of September 28, 2026.

What's New

Additional reporting provides further context on the warming trends. Winkley said San Antonio now averages 21 more days of above-average temperatures than it did a few decades ago. San Antonio's average fall temperature has increased by 3.8 degrees since 1970, as reported by Climate Central.

Winkley noted specific impacts of the warming. Warmer weather can lead to higher utility bills as residents use air conditioners longer into the fall season. Warmer temperatures can extend mosquito activity and make allergy seasons last further into October and November.

Warmer overnight temperatures can affect the timing of fall foliage. Regarding the magnitude of the change, he stated, "Like a 4-degree temperature swing from Monday to Tuesday isn’t that big of a difference. But when you’re looking at this long-term trend, that’s essentially like your body temperature going up 4 degrees. You would be in the hospital." According to ExpressNews, Nielsen-Gammon said after reviewing San Antonio weather data that August was the second warmest on the books and the combined August and September together was the warmest on record, about 5 degrees above the long-term average.

How Sources Differ

Sources present different metrics regarding average temperatures. Shel Winkley, a meteorologist at Climate Central, said San Antonio now averages 21 more days of above-average temperatures than it did a few decades ago. Climate Central reports that San Antonio's average fall temperature increase of 3.8 degrees since 1970 aligns with a 21-day extension of above-average temperatures, as reported by Climate Central.

Why It Matters

The record-breaking heat in San Antonio reflects a broader pattern of fall warming driven by climate change. The 3.8-degree increase in average fall temperature since 1970 represents a shift in the local climate, with fall identified as the third fastest-warming season in the city's history. This trend results in 21 additional days of above-average temperatures compared to previous decades, extending the period of heat exposure for residents and ecosystems.

The prolonged warmth carries concrete consequences for public health and infrastructure. Extended mosquito activity and longer allergy seasons pose ongoing health challenges, while increased air conditioner usage drives up utility bills for households. The disruption of fall foliage timing and effects on Hill Country ecosystems illustrate the environmental stakes. With severe weather and flooding threats emerging as the heat breaks, the region faces a transition from extreme heat to potential water-related hazards, reflecting the complex impacts of a changing climate on daily life and safety.