Severe weather continues across the Plains and the Midwest, with the threat of damaging storms extending Thursday from Texas to North Dakota.
Meanwhile, forecasters warned the atmosphere is primed to produce violent tornadoes.
The National Weather Service warned the greatest threat for twisters will be in Oklahoma and Missouri.
Some of the same communities devastated by the storm that hit Oklahoma last week are once again in danger.
"I think it's coming our way," one Oklahoma resident said. "Hopefully we have a few hours before it gets here."
Forecasters say the storms are developing ahead of a cold front. The clash between the cool air and the warm, humid air already over much of the Midwest creates a ripe environment for tornadoes.
It also brings lots of rain and massive flooding, and Iowa has seen the worst.
Several rivers in the state have already reached record high water levels.
There's also flooding up and down the Mississippi as rain swells the mighty river.
The water is rising in unexpected places, such as in several Chicago neighborhoods after a major storm. A burst of water pushed through the doors of an Illinois college.
The storm front is expected to move east over the weekend, but parts of New York and New England are already experiencing severe weather.
"Every car has pulled over and put their hazards on -- definitely no condition to be driving out at this point," one resident said.
Strong winds brought down trees in Rotterdam, N.Y., damaging homes, cars and downing power lines.
Meanwhile, summer weather is arriving on the East Coast Thursday, with temperatures expected in the 80s and 90s from New England to Florida.