The below freezing temperatures took many by surprise.
"If a penguin came here, he could probably stay here," Brandon Nelson, of Fargo, explained of the sub-zero temperatures outside.
Inside a freezer, the temperature is about 20 degrees, which means temperatures outside are at least 25 degrees colder than that.
A relatively mild winter might be to blame for these shocking temperatures over the next few days.
Being active in the weather can be dangerous. Doctors at Sanford say muscle fatigue combined with breathing in this cold air can make for what feels like a miniature asthma attack.
So, to answer the question, how cold is it? Your best bet might be to sit this one out and let someone else tell you.
"Stay indoors, or if you do go outside wear a jacket, a very big jacket," Nelson said.
Temperatures will drop low enough in the next few days to have some fun with the weather by trying some science experiments like turning boiling water to snow.