It's a sign of spring on the Big Sioux River.
Heavy rain to the north has pushed the river to flood stage near Akron, Iowa.
The river is expected to crest just more than 18 feet at 1 A.M. overnight.
Aerial video shows thousands of acres of farm land are flooded in the area.
The river won't affect any homes or roads unless it pushes 2 to 3 feet higher.