The National Hurricane Centre says Harvey is back on land after coming ashore early today just west of Cameron, Louisiana.
The tropical storm is expected to weaken and continue to the north.
The storm returned to land about five miles west of Cameron with maximum sustained winds of 45 mph.
Centre meteorologist Dennis Feltgen said on Tuesday that when Harvey came back to shore, "it's the end of the beginning".
Harvey is forecast to drop substantial amounts of rain on Louisiana before moving on to Arkansas, Tennessee and parts of Missouri - which could also see flooding.
Mr Feltgen said there are still a lot of residents in multiple states "who are going to feel the impacts of the storm".
Harvey first made landfall on Friday in Texas as a Category 4 hurricane.