The people who were injured, none seriously, were at Weimar High School's football field, where pizza was being sold for a fundraiser when the storm hit, KTRK-TV, Houston, reported.
"Shingles were flying off the roof of the building of the school," Weimar High School junior Peyton Wunderlisch said. "If you look down the football field, the press box, the football field, just was gone, so all that was blown away in an instant and we had no idea what was going on at the time. We were just scared."
A pizza trailer was overturned and KTRK was told a cemetery near the school sustained some damage.
Colorado County Judge Ty Prause said a train was derailed and a Weimar hospital sustained enough damage that patients had to be evacuated to other hospitals.
A dozen sightings of tornadoes were reported in an area east and southeast of San Antonio to the Gulf Coast, AccuWeather.com reported. Several storms produced damaging winds and large hail.
Between 1.5 and 2 inches of rain fell across parts of San Antonio, with some areas outside the city reporting up to 6 inches of rain, submerging several roads, AccuWeather.com said.
In Austin, officials said heavy rain led to flooding that closed many roads.
Eastern Texas could get up to 3 inches of rain before the system moves into the Lower Mississippi Valley Saturday, AccuWeather.com meteorologists said. Areas along Texas' Gulf Coast could see isolated amounts of 4-plus inches.