Fall in San Antonio has become nearly 4 degrees warmer since 1970

Fall is the third fastest-warming season in San Antonio, and heat-trapping emissions are playing a role in the warming trend

Leah Rodriguez, KSAT Weather Authority Meteorologist

Published: September 25, 2026 at 3:50 PM

SAN ANTONIO – Meteorologist Shel Winkley of Climate Central said San Antonio now averages 21 more days of above-average temperatures than it did just a few decades ago.

Average daytime highs typically drop from the low 90s to the low 70s during meteorological fall, which includes the months of September, October, and November. Unfortunately, temperatures are not cooling as quickly or staying as cool as they once did.

Climate Central found that San Antonio’s average fall temperature has increased by 3.8 degrees since 1970.

“Three-point-eight degrees may not sound like a lot,” Winkley said. “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.”

Warmer temperatures can have a much larger impact than causing changes to your wardrobe. A longer stretch of heat can extend mosquito activity and make allergy seasons last further into October and November, Winkley said.

Warmer weather can also mean higher utility bills as residents keep their air conditioners running longer into the fall season.

Your travel plans to see fall foliage can also be affected.

Overnight temperatures have warmed the most compared with historical averages. Cooler nighttime temperatures help signal trees to prepare for winter, so the added warmth can affect the timing of fall foliage.

South Texas typically sees fall colors later in the season, but across other parts of the country, warmer fall temperatures are delaying the arrival of those fall colors.

How climate scientists measure changes to our climate

The development of attribution science examines how human-caused emissions affect the likelihood and frequency of extreme weather.

Climate scientists run more than 20 models using historical emissions, including the heat-trapping pollution released by humans. They then run the models again after removing the human contribution to compare current conditions with what would be expected from natural weather variability alone.

That comparison produces a ratio showing how much more likely an event is because of climate change. The scale generally ranges from zero to five. A rating of four means a temperature event would have been rare without climate change, while a rating of five means it would have been nearly impossible without the influence of human-caused emissions.

That does not mean climate change caused every degree of heat, Winkley said. Instead, it makes unusually warm temperatures more likely and causes them to happen more often.

“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,” Winkley said.

Whether you choose to call it climate change or not, fall temperatures are trending warmer as a result of heat-trapping emissions building up in the atmosphere.