Flash flooding across southern states and the Midwest as of Monday has killed at least 21 people. 

At least half of the deaths have occurred in Tennessee, three others were in Missouri and two were in Kentucky.

Deaths have also been reported in Arkansas, Georgia and Mississippi, but it is unclear the number in those states. 

Some of the deaths include elderly people and children. In Kentucky, a 9-year-old boy was killed by floodwaters while waiting at his bus stop. 

As of Monday afternoon, about 9 million people in the U.S. were under a flood watch. 

The flood threat is likely to end Monday evening but the Pacific Northwest is expected to be hit with new storms throughout the week, according to NBC News.