"Hail and extremely high winds uprooted a large tent" at the Wood Dale Prairie Fest this afternoon, according to the Wood Dale Police Department Facebook page.
One person was killed and 15 people were hospitalized, police said.
The police called it a "tragic accident" and said the incident is under investigation.
"Our most sincere thoughts and prayers go out to those affected by today's event," the police wrote.
Today was the last day of the four-day festival, which includes live music, a carnival and fireworks, according to the city.
Police said the rest of Prairie Fest has been cancelled.