"That's when we saw this huge tornado ... the biggest one I've ever seen in my lifetime," he said. "My son and I both said, 'Wow, this is huge.' It was moving extremely fast. You could definitely tell it was heading right towards Parkersburg."
Like McMillan, Wolthoff was shocked at both the appearance and the size of the tornado. "It was not like your normal tornado funnel cloud that you would normally see photos of or on TV. This was just a huge, looked like a massive cloud that was rotating," he said.
McMillan, as well as other storm spotters, alerted local authorities, who directed the fire department to set off tornado sirens. Fatefully, the town had installed a second siren a few days earlier in the part of town near the tornado's path.
"It actually was practiced with, the day before our tornado hit," Parkersburg Police chief Chris Luhring said. "They practiced initiating that siren on Saturday, less than 48 hours before our tornado hit."
Meanwhile, with first responders already on alert, Wolthoff monitored the storm's movement and captured it on video.
By this point, there is nothing that the people of Parkersburg can do but take cover. In fact, people had just 8 minutes after the sirens started blaring until the tornado hit.
The pace of the tornado, as well as vigilant first-responders, was breathtaking. The first tornado touched down at 4:47 p.m., east of the town of Ackley. At 4:51 p.m., Parkersburg's tornado sirens began to wail. At 4:59, the tornado hit Parkersburg.
"There was only a very small window for people to recognize how strong of a storm this was and take appropriate action," McMillan said.
As terrifying as it looked, the brute force of the storm was even worse. Parkersburg was struck by the strongest and most dangerous type of tornado, known as an EF5. For earthquakes, there's a 10 on the Richter Scale and for hurricanes, there's a Category Five. When it comes to tornadoes, an EF5 is, quite simply, as bad as it gets.
"We're talking serious winds, stronger than Hurricane Katrina, 200-plus, mile-an-hour winds," McMillan said. "As spotters, it blew us away, we knew [an EF5] could happen. We didn't realize it could happen that fast."
The unbelievable force of the Parkersburg tornado, which grew to be three miles wide and cut a 40-mile path of destruction through Iowa's plains, leveled more than 250 homes and erased more than 20 businesses.
Perhaps most remarkable, though, is that relatively few people were killed. With damage like this, the toll could have been massive, but only nine people died.
McMillan remembers the feeling of dread that washed over him after the tornado passed.
"You thought that everyone had died," he said. "We thought hundreds of fatalities at first. We thought … no one had made it through that tornado in that damage zone."
As he and his fellow storm spotters rode into town after the storm, their fear grew as they anticipated a high number of casualties. "If they didn't get out of the way of the storm, they weren't going to make it through," McMillan said. "This is, truly, a storm that no one wants to ever face in person."