Preliminary data indicates it was an EF3 tornado, the weather service said, stronger than the EF2 estimate they made Monday.
Texas Hill Country is often referred to as "Flash Flood Alley."
The governor of Missouri has declared a state of emergency on Friday in response to flash flooding in central, south-central and southeastern parts of the state.
El Niño is officially on the rise. Ocean temperatures along the equatorial Pacific are running 1.2°C above average, and forecasters say warming is expected to continue into winter.
At least four people are dead amid flooding caused by heavy rains in Kentucky, Governor Andy Beshear said Saturday.