MINNEAPOLIS (WCCO) — It seems like the video of those flying trailers has been played on repeat since Tuesday’s tornado hit in Dallas, Texas. Perhaps it’s because it’s a phenomenon difficult to understand. So, how did a tornado make those trailers fly? Good Question.

Before we can understand exactly what made these 20,000-pound semi-truck trailers fly, we must start with the basics.

In severe thunderstorms, tornadoes form when updrafts of warm, humid air start to rotate, creating a vortex. Things underneath that vortex will be taken up with it because the winds are so strong.

University of Minnesota Physics professor Dan Dahlberg says those winds can reach speeds up to 300 mph.

“The air is flowing so fast that they don’t have much choice but to go with it,” said Dahlberg.

The lift is caused by the fact that high pressure — the ground — meets low pressure, which is the tornado.

“Suction is a common word that we use, but it’s really because you have a pressure imbalance,” said Dahlberg.

As a result– the semis are pulled up into the air stream– and the spinning vortex gives them something to sit in.

“That’s because there’s strong air currents that are moving up and it’s actually that drawing, those strong air currents going up, that’s pulling things up in there, and the fact that it rotates just adds some stability to this whole process,” said Dahlberg.

Even Dahlberg says he’s still fascinated by its strength.

A lot of us have heard opening windows could help save your house in a tornado because of that pressure difference. The idea is that all that built up pressure could make the windows blow out. But that’s not the case. Bottom line, just stay away from the windows because that’s the most dangerous place to be.