A flash flood emergency has been issued for the Midwest and South as forecasters warn of a 'historic' deluge - with up to 21 inches of rain expected in some areas

A day after parts of the Midwest and the South were bombarded with severe thunderstorms, hail and tornadoes, another round of storms — and life-threatening flash flooding — has been forecast for the region.

Fears grow as a 'one-in-1000 year' storm is brewing, threatening to unleash unprecedented rainfall across the Midwest and South.