At least one tornado touched down late Tuesday near Anna, a town of about 6,500 residents north of Dallas, said Jamie Nicolay, of the Collin County homeland security and health care services department. Severe weather was also reported in Westminster.
The dead included an elderly couple and a teenager, but their identities have not been released, Nicolay said.
Six people were transported to area hospitals, she said. Their conditions were not available.
The storm destroyed at least six houses, Nicolay said, although full assessment of damage to the area was limited by darkness.
"I'm sure that there are numerous other ones that have less severe damage," she said.
More than 100 rescue and utility workers had responded to the area to assess the damage and work on restoring power to about 300 homes.
The American Red Cross has opened a shelter at Anna High School.