Good morning, NBC News readers.

This Tuesday morning we're looking at the destruction left in the wake of severe weather that tore through parts of Ohio overnight.

Plus: could schools move to a four-day week? One school district in Colorado tried it — but parents are not impressed.

Here's what we're watching:

Tornadoes cause severe damage in Ohio

Heavy tornado damage near Interstate 75 in Dayton, Ohio, on Monday night. Jordan Lynn Freshauer via Facebook

At least seven people were injured as extreme weather left thousands without power across Ohio overnight.

The mayor of Celina, in Mercer County, said parts of the area look "like a war zone, some of the houses were completely moved off their foundations and gone."

Here is NBC News' article with the latest.

2020 Democratic presidential candidates: U.S. Senators Bernie Sanders, Kamala Harris, Elizabeth Warren, Cory Booker, Amy Klobuchar, Kirsten Gillibrand, and Michael Bennet, former Texas congressman Beto O'Rourke, U.S. Representatives Tulsi Gabbard, John Delaney, Eric Swalwell, Tim Ryan, Seth Moulton, and former HUD Secretary Julian Castro, Mayor Pete Buttigieg, Former Gov. John Hickenlooper, Gov. Jay Inslee, Andrew Yang, Marianne Williamson, Mayor Wayne Messam, and former U.S. Vice President Joe Biden. Reuters file

How many of the candidates running in the Democratic primary could you name? If the answer is "not very many," then you're not alone. It's the most crowded presidential primary field in history.

But this is a problem: voters could be facing what political scientists call "choice overload," in which they ignore most of the field and opt for the best-known candidate. Which may explain the stronger-than-expected start for Joe Biden. Read more here.

Kids and teachers love the idea of a four-day school week — but parents don't

Prairie View High School seniors cheer during their "Moving Up Assembly" at Prairie View High School in Brighton, Colorado, as the school completed its first year after instituting a four-day school week. Rachel Woolf / for NBC News

If your children struggle to find the enthusiasm to get up and go to school on a Monday morning, there may come a time when they don't have to.

NBC News' Adam Edelman reports that one school district in Colorado switched to a four-day week at the start of this school year. Students spend their Mondays playing volleyball, spending time with family at the local state park or volunteering.

It's a move designed to attract and retain teachers — but of course not everyone's happy. Parents of younger children worry about childcare while those with older kids are concerned about too much unstructured time.

Adrian Lam / NBC News

If you ever receive automated phone calls telling you about something that sounds very much like a scam, you're not the only one.

The Federal Trade Commission received more than 3.7 million complaints about this last year and a Freedom of Information request by NBC News uncovered just how fed up Americans are with these scam calls.

"It is harassment we are compelled to endure in order to own a phone. DO SOMETHING!" is how one angry consumer summed up their feelings. Read more from NBC News' Allan Smith.

Activist campaign urges Trump impeachment

Speaker Nancy Pelosi, D-Calif., greets supporters last Friday at Delaware County Community College in Media, Pennsylvania. Matt Slocum / AP file

A new campaign kicks off Tuesday pressuring Democratic congressional leaders to start impeachment proceedings against President Donald Trump.

Stand Up America says it has 2.4 million members and is set on lobbying members of the House. Key figures, such as Speaker Nancy Pelosi, have called for patience as all options are tried before impeachment, such as using contempt rules against those who defy subpoenas.

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Plus

Almost 15 percent of teenagers treated in an emergency room were given a prescription for opioids in the 10 years to 2015, a new study has found.

Trump wished U.S. service members aboard an American assault ship docked in Japan a "happy Memorial Day."

A 61-year-old American climber died while making the descent from the summit of Mount Everest on Monday, Nepali authorities confirmed.

Confused but curious about the results of European Parliament elections? This explainer picks out five crucial themes

Former celebrated baseball star Bill Buckner has died at the age of 69, his family said.

THINK about it

Young people can often struggle maintain friendships once they transition into adulthood, especially after moving because of college or for a career.

But there are things they can do to mitigate this and retain strong bonds, writes Janice McCabe, an associate professor of sociology at Dartmouth College.

Science + Tech = MACH

Are aliens creating alien-human hybrids to combat climate change? There's no evidence they are but, bizarrely, this is an argument being made by a languages expert at the University of Oxford.

Young-hae Chi's claim has attracted much attention in the U.F.O. community. And Chi tells NBC News that we can't spot these hybrids because they look just like us.

Quote of the day

"I saw the clouds spin backwards and the trees began to sway uncontrollably and we took shelter. I was standing on the porch that is no longer standing.”

— Dayton resident Tenley Taghi, on the devastation caused by a tornado overnight.

One fun thing

The Grand Canyon National Park celebrates its 100th anniversary this week.

It's happy birthday to Grand Canyon National Park, which has just turned 100. Some six million visitors a year flock to see the natural wonder and enjoy one of the darkest night skies in the world.

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