El Reno, Okla. — The central U.S. is stuck in a cycle of dangerous storms that won't stop anytime soon. Tornadoes struck again Monday in Iowa, Illinois and Indiana — and more may fire up later.

In the past week, at least 15 people have been killed by tornadoes and flooding.

Rivers are rising to record levels, threatening homes and businesses in Arkansas, Oklahoma, Kansas and Missouri.

More severe weather slammed the Midwest on Monday afternoon in Illinois, where heavy rain and hail hammered the town of Yorkville.

A gas station in Illinois destroyed by severe weather Mon., May 27, 2019. CBS News

A tornado touched down in Iowa.

A tornado seen in Iowa on Mon., May 27, 2019. Kevin Hennick

Over the past few weeks, spring storms have soaked the nation's midsection. Drone video shows the scope of the historic flooding along the Arkansas River near Fort Smith, neighborhoods and cars submerged.

And the worst is yet to come.

The river is expected to crest Wednesday — a historic 20 feet above flood stage. Residents aren't just worried about keeping the water out. Barling Police Oofficer James Breeden said they're keeping an eye on the levees.

"There's concern about the integrity of the levees. They've never been tested to this limit before," Breeden told CBS News.

Donna and Jerry Morgan spent Memorial Day delivering sandbags to people bracing for the rising water.

"It's dire. Dire. I mean these people are suffering," Donna said. "They're losing everything, they're losing their homes."

Over the weekend, an EF-3 tornado packing winds up to 165 mph, cut through El Reno, Oklahoma, where it killed two people and injured more than 25 others.

On Monday, Oklahoma Gov. Kevin Stitt got a call from President Trump while he surveyed the damage.

It's just unbelievable that a tornado can do this type of damage," Stitt said. "It doesn't do it justice when you see it on TV ... it's just unbelievable anybody could survive."

While the cleanup continues, there are more storms in the forecast.

There's a threat Sunday night from Nebraska to Indiana.

Over the next 48 hours, there's a chance of flash floods and tornadoes from Oklahoma to Kentucky. On Wednesday, the severe weather threat extends south of Dallas. The heat wave in the Southeast is expected to continue thru Wednesday.