Remember the polar vortex back in early 2019? It’s not every day that your hometown is colder than Antarctica, right?

So it is for residents of Chicago, Illinois, as they dealt with the Arctic blast that caused the Chicago River to start icing up. It wasn’t pretty. The subzero temperatures forced people to stay indoors for their own safety, but curiosity still wins.

Twitter user @ARobertsJourno decided to toss a mug of boiling water into the air to demonstrate how incredibly cold it was in the Windy City when temperatures dropped between -20 and -15°F. Watch the clip to see exactly what happens.

In what looks like a specter of magical vapors, the water is no longer water. Scientists state that when cold air meets warm water, it changes the form of the liquid, essentially turning it into a foggy mist. Cool, huh?

Images shared on social media of the Chicago River show the same “smoky” effect happening on the water’s surface. At that moment, the river was warmer than the air above it!

Were you expecting the water to do that? Have you tried similar experiments when the weather was wacky?