At least 16 people are believed to have died after tornadoes, heavy rain and flash flooding battered parts of the South and Midwest in the United States. Among them was a 9-year-old boy, who was swept away while walking to a school bus stop in Kentucky on April 4.

About 22 million people are at risk for severe storms Sunday, stretching from central North Carolina southwestward to the central Gulf Coast, according to the Storm Prediction Center.

Day after day of heavy rains have pounded the central U.S., rapidly swelling waterways and prompting a series of flash flood emergencies from Texas to Ohio.