Hurricane conditions will continue along the southern coast of Texas before the storm weakens into a depression later on Sunday, according to the weather forecast.
Hurricane Hanna may cause isolated tornadoes along the southern coast of Texas, the US National Hurricane Centre said on Saturday.
Heavy rains and flash flooding are now impacting portions of the Texas coast from Port Mansfield to Sargent, where a storm surge warning has been issued.
Tropical storm Hanna was upgraded to a hurricane on Saturday morning, located about 115 kilometres (70 miles) south of Corpus Christi in Texas, and bringing winds of 150 kph (90 mph), according to the NHC.
Hanna is the first hurricane of the 2020 Atlantic season.