Potentially historic flooding is underway Thursday in the Mississippi and Ohio valleys, as repeated rounds of rain pummel several states in America’s heartland.

A massive storm hitting the central U.S. on Wednesday could spin up damaging tornadoes and dump heavy rain from northern Texas to the Great Lakes.

Parts of the Mississippi Valley are already inundated, with the potential for once-in-a-lifetime rainfall and widespread impacts, "generational flooding" is possible across parts of the nation through Saturday.