Record rainfall and severe thunderstorms will mean a heightened risk of flash flooding across the south-central United States through early Thursday.

Slow-moving thunderstorms dropped record rainfall across much of southern Oklahoma and northern Texas Wednesday, triggering flash flooding and forcing evacuations, as residents in Pennsylvania and Ohio picked up from a powerful storm that left more than half a million customers in the dark.

A least one person died when his vehicle was swept away by floodwaters in Oklahoma on Wednesday as slow-moving thunderstorms inundated roads across parts of that state and Texas, authorities said, while Pennsylvania residents picked up from a powerful storm that left three people dead.