The areas of impact include George West, Lake Bryan, Wixon Valley and Mooring.
Residents have been told to seek shelter at low points.
Wind and hail damage is expected to affect vehicles, roofs and trees.
Tornado HQ said: “For your protection move to an interior room on the lowest floor of a building.
“Torrential rainfall is occurring with this storm and may lead to flash flooding.
“Do not drive your vehicle through flooded roadways.
“Mobile homes will be damaged or destroyed.”
More to follow…