Authorities rescued two drivers whose cars became submerged less than half a mile apart from each other in San Antonio.
Isolated locations saw 4-5 inches of rain from the storms in a few hours time.
On Monday morning, crews were called to a water rescue after a man driving his SUV got trapped in rushing water along a San Antonio street.
Emergency teams in San Antonio are trying to reach people stranded by intense flooding.
Officials say several homes were evacuated due to the severe weather and residents in low-lying areas are being urged to find shelter. Some cars were even seen stuck in the water.
Firefighters attempted to extend a unit ladder to the young man.
Caught on video, firefighters had to extend their ladders as far as they could go, with the man clambering from the roof of his vehicle to the ladder.
Drivers should not try to cross a road when there's water running across it.