A new study on rain events in Texas could help reduce urban flood risks and improve planning for extreme weather.
The Texas A&M Urban Flood Study found that cities can actually change the weather, depending on the type of weather event.
Researchers looked at over 40,000 warm‑season individual storm events in Dallas-Ft. Worth, Austin, Houston and San Antonio between 1995 and 2017.
The study looked at individual storms instead of long-term rainfall totals and sorted storms into distinct categories, tracking their three‑dimensional structure using weather radar.
Researchers found that cityscapes and urban areas strengthen some storms while weakening others.
Dr. John Nielsen‑Gammon is a Texas A&M University atmospheric scientist and a co-author of the study. Nielsen-Gammon is also the Texas State Climatologist.
He said the most dangerous types of urban storms are ones that are similar to the June 2025 San Antonio flood which killed 13 people.
“That sort of rainfall runs off quickly and can potentially overwhelm sewer systems and urban creeks and streams and culverts.”
According to an overview of the study, the strongest and most consistent urban effect appeared in small‑scale thunderstorms, the kind that can pop up quickly on hot summer days.
Across all four cities, these local storms occurred 7% to 31% more often over urban areas than over nearby rural land. Radar data also showed that these storms tended to grow taller and more intense over cities, a sign of stronger upward motion in the atmosphere.
Cities can create what are referred to as “urban heat islands” which can cause storms to be more intense.
Nielsen-Gammon said many people incorrectly think that cities “repel” storms, or make storms go around them.
“People tend to perceive that cities inhibit rainfall, and actually that’s true of people just about everywhere. They often ask me why do storms seem to go around them rather than hitting them,” he said.
A copy of the study is here. I’ve not had a chance to look at it, but I hope the Mayors of those cities has someone reading it over carefully. We know about heat islands and how temperatures can vary greatly within a city, both of which will be getting worse in the absence of action. We also know that the costs of flooding affect us all one way or another. There’s no escaping the expanding flood map. Whatever cities can do to lessen those effects will have far-reaching consequences.