The governor made the request Tuesday in a letter to President Barack Obama.
Nixon notes that the Missouri has already caused extensive flooding and is expected to threaten 25 counties in all, from the far northwest to St. Louis. He says flash floods have also affected Clark and Lewis counties in the northeastern part of the state.
Nixon's request specifically asks for federal assistance in operations to save lives and property, including material to support long-term shelter operations. He's also requesting help and equipment for flood-fighting operations, such as pumps, sand and sandbags.