The storm, which has even stronger gusts, is expected to be the worst to hit Texas for 12 years. Up to 40in (1m) of rain is expected to fall.
President Donald Trump has signed a disaster proclamation for the state, which will free up federal aid for the worst-affected areas.
Texas Governor Greg Abbott has warned of record flooding in multiple regions.
The category four storm has already brought down trees in the city of Corpus Christi and thousands of residents have boarded up their homes and fled.
The mayor of nearby Rockport, Patrick Rios, urged the few people in the town’s population of about 10,000 people not already to have evacuated to do so immediately.
The city manager said people were trapped in a housing centre for elderly people, where the roof had collapsed and rescue teams were unable to gain access, according to CBS.