Why is South Central Texas’ geography so unique? KSAT Explains

From the Balcones Escarpment to the Hill Country to the coastal plain, there’s a lot to love

San Antonio sits at the crossroads of several different geographical regions, with the Balcones Escarpment being a main player in why South-Central Texas is the way it is.

Never Eat Soggy Waffles. Remember that one? Or maybe it was Never Eat Shredded Wheat. Either way, those rather unappetizing mnemonics helped us learn our cardinal directions back in grade school.

It’s helpful to know your directions when watching KSAT’s weathercasts. But, you’ve probably also noticed that we throw out quite a bit of geographical jargon when giving the forecast. So, for this KSAT Explains we are diving deep into the fascinating geography of South Central Texas. To start, let’s see how much you know...

How did you do? Whether you’re a master of geography or not, there’s really only one feature that ranks most important for shaping the area where we live: the Balcones Escarpment.

”This is a major uplift that happened about 24 to 25 million years ago when we actually had a big chunk of central Texas lifted up around 1500 feet,” explained Dr. Thomas Adams, Chief Curator at the Witte Museum.

The escarpment is a U-shaped boundary that features porous limestone and was formed by an ancient ocean. It’s why we have an aquifer and it’s responsible for the prolific springs that dot the central and south Texas landscape.

”Without the springs, you wouldn’t have San Antonio,” said Dr. Harry Shaeffer, Curator of Archeology at the Witte Museum.

The rise in elevation along the escarpment can also make a difference when it comes to weather. More on that in a moment. But, the Balcones Escarpment is the reason we have the Hill Country. That’s a term we throw around a lot.

What is the Hill Country and how is it different from the Edwards Plateau?

”The Hill Country is just part of the Edwards Plateau,” said Adams. “It’s sort of the eastern edge of that plateau. It really encompasses that edge, plus the Balcones Escarpment coming down into San Antonio.”

Which brings us to Interstate 35. It’s a major, important thoroughfare. But, have you ever noticed how it seems to line up with the edge of the escarpment?

”The I-35 corridor is actually just on the eastern side of the Edwards Plateau,” said Adams. “So, instead of building up and over the plateau they just went around it.”

That, and going back to the importance of the springs along the escarpment, major cities formed right along these water sources and the interstate connected them. Cities like Austin, San Marcos, New Braunfels, and San Antonio developed in these zones.

Since I-35 serves as a visual boundary of the edge of the escarpment, we often use it during our weather segments to divide up different climate zones. You may hear us say, “People who are east of I-35 have the best chance for rain,” or, “People who are west of I-35 have a higher fire danger today.”

Similarly, Highway 90, which runs west to east, is useful too. San Antonio literally sits at a geographical crossroads.

”San Antonio is at the point of three different major eco-regions: the South Texas thorn brush, which basically starts in San Antonio and goes south to the Valley,” explained Helen Holdsworth, Chief of Engagement at the Witte Museum.

That’s more or less an extension of the Chihuahuan Desert, which creeps into our area from the west. Think dry and hot.

“Then we have the Hill Country, which goes from west of town toward Kerrville, Sonora,” added Holdsworth.

It’s the elevated portion of our viewing area that we mentioned earlier.

“And then we have the Plains, the Central Prairie,” said Holdsworth.

That’s the flatter part of South Central Texas, closest to the coast. It features higher humidity, more rain, and more vegetation.

”You drive any direction and you’ve got a different scene.” added Holdsworth.

With all of that in mind, let’s do some myth-busting — deciphering fact from fiction when it comes to geography, and what it means for our weather.

  • FACT: Clouds do bank up against the escarpment, occasionally making it cloudy in San Antonio, but sunny in the Hill Country. The escarpment can, at times, help to develop light showers or slightly enhance rainfall.
  • FICTION: No, there’s not a dome over San Antonio. Any sort of heat island effect has no bearing on storms moving through or avoiding the city, despite recent claims.
  • FACT: Yes, those east of I-35 often have better chances of rain because they are closer to the Gulf of Mexico and therefore have better, deeper moisture.
  • FICTION: No, valleys and terrain don’t prevent you from experiencing a tornado. In most cases, they develop and move as they please.
  • FACT: Yes, the Serranias Del Burro, mountains west of Del Rio in Mexico, do have an effect on our weather. They give a lift to big storms in the summer that can sometimes cross into Texas.
  • FICTION: No, there’s no one-favored area in San Antonio that gets hail over another.
  • FACT: Yes, geography does play a role in winter weather, with northern Bexar County, especially north of 1604, having a better shot at seeing wintry weather than those in southern Bexar County.

This is why being a meteorologist in South Texas is so fun. Lastly, we must talk about counties. County boundaries are more political than they are geographical, but useful when we are describing where a thunderstorm is located. It’s always a good idea to know where your county is located on a map. When severe weather rolls around, we identify the storms based on which county they are moving through.

That is South Central Texas geography in a nutshell. It’s also why reading an atlas isn’t as boring as you might think!

About the Authors:

Justin Horne is a meteorologist and reporter for KSAT 12 News. When severe weather rolls through, Justin will hop in the KSAT 12 Storm Chaser to safely bring you the latest weather conditions from across South Texas. On top of delivering an accurate forecast, Justin often reports on one of his favorite topics: Texas history.

Valerie Gomez is lead video editor and graphic artist for KSAT Explains. She began her career in 2014 and has been with KSAT since 2017. She helped create KSAT’s first digital-only newscast in 2018, and her work on KSAT Explains and various specials have earned her a Gracie Award from the Alliance for Women in Media and multiple Emmy nominations.