AMNA NAWAZ: While flooding along the Mississippi River happens every year, water levels are surging this year, thanks to a record snow across the Midwest that's been followed by a sudden thaw.

William Brangham reports.

WILLIAM BRANGHAM: Last fall, drought shrank the Mississippi to historic lows.

Now it's the opposite problem.

Water levels are hitting heights not seen in decades.

Communities up and down the Mississippi are inundated, stretching from St. Paul, Minnesota, to just north of Saint Louis, Missouri.

In Eastern Iowa, some streets appear as if they're a part of the river.

The city of Davenport's ballpark is surrounded.

But Davenport Mayor Mike Matson said his constituents are resilient.

MIKE MATSON, Mayor of Davenport, Iowa: There's certainly folks impacted.

And the American Cross and us work directly, the Salvation Army, others.

And we have a shelter for those that would like it.

We provide some assistance.

And we asked for a declaration, emergency declaration, and our governor granted that, so people can get individual assistance.

WILLIAM BRANGHAM: Is this a challenge for you all trying to plan a city that you want to stick around for generations to come when you're never quite sure whether the river is going to be low or whether it's going to be coming into your living room?

MIKE MATSON: We are a little bit concerned, as it seems maybe some of the storms, the precipitation levels or amount seems to be continuing to grow or increase in intensity.

That's certainly something we need to keep an eye on.

And we're always talking with our folks at the federal level about that.

WILLIAM BRANGHAM: This recent flooding comes after the Upper Midwest experienced record winter snows.

And when April suddenly turned warm and did so fast, that melting snow sent a gusher into the river.

Jason Knouft is a freshwater scientist at Saint Louis University.

JASON KNOUFT, Saint Louis University: I always say that water touches every part of our lives.

And when we see flooding, when we see droughts, it disrupts supply chains.

We saw that last year in the Mississippi River with droughts.

And, this year, we're seeing it with these severe floods across the Upper Mississippi Watershed.

And the challenge that we face is that this is what we're expecting with climate changes is greater variability in weather patterns.

And we often think, well, this is the new normal.

And it's -- unfortunately, it's not the new normal.

Next year is going to be different.

The year after that is going to be different.

And the year after that is going to be different.

And it makes it very hard to plan.

WILLIAM BRANGHAM: In Stillwater, Minnesota, the water crept right to the edge of houses and local businesses.

Now the cleanup begins.

Stillwater Mayor Ted Kozlowski: TED KOZLOWSKI, Mayor of Stillwater, Minnesota: It's always been a badge of honor in Stillwater to help sandbag, right?

Rite what's kind of concerning is, I just -- there's a delta somewhere where, does it make sense to keep doing these kinds of temporary preparations, or do we, as a city or a state or as a -- from the fed gov, have to bite the bullet and say, you know what, we need to do something permanent along the shoreline of our river community, of other river communities?

WILLIAM BRANGHAM: The river levels now seem to be receding.

The hope is that the rest of that northern snow melts at a more manageable pace going forward.

For the "PBS NewsHour," I'm William Brangham.