There are reports of multiple people being swept away by flooding in Virginia as tens of millions of people are at risk of dangerous flash floods in pockets of nearly every region of the contiguous United States Friday,

Most of the country was blanketed by yellow rain and thunderstorm warnings, with the Met Office saying this could bring flash flooding, power cuts and disruption to travel. But the flooding forecast for London and south-east England on Saturday morning did not occur.

“If you’ve never seen water rise in front of you in minutes, it’s hard to conceive of how quickly that can happen—and how quickly your life and property can be at risk,” said Rachel Hogan Carr, executive director of the Nurture Nature Center, a nonprofit focused on flood-risk communication.