The relentless rain also caused a dam to fail, creeks to overflow and roads and highways to close across the state.

Slow-moving thunderstorms across parts of Oklahoma and Texas flooded roads and forced evacuations on Wednesday as residents in Pennsylvania and Ohio picked up from a powerful storm that left more than half a million customers in the dark.

Severe weather in Oklahoma has left four people dead, including a 12-year-old boy and his mother, officials say.