Then, with the wind blowing, it made it bone-chilling.
With a low temperature of minus nine, the wind chill in St. Joseph got down to negative 29 degrees Monday morning.
In what was supposed to be the first day back from holiday break, St. Joseph schools were closed Monday morning.
It's no surprise given just how cold the air was, and how cold the wind chill became.
Steve Huff from the St. Joseph School District explained that decision-making process in an interview from Friday:
"We've had a cold weather rule in effect since the late 1990s," Huff said. "The cold weather rule is a two-pronged attempt at being objective on making cold weather decisions. There are two criteria in play: one it has to be zero degrees in air temperature and then the wind chill has to be minus 20 or more."
Mike July, Senior Forecaster from the National Weather Service Pleasant Hill, says that the higher the wind, the colder I feels on your skin.
"What's happening is the wind is taking away the body heat that you have on that exposed skin, and making it feel colder than the actual air temperature," July said. "So the wind is in effect taking away the heat and robbing the heat away from the body that's exposed."
The formula to determine wind chill is actually a little bit complicated.
But this graph shows that with wind chill values like Monday morning, frostbite can occur in 30 minutes or less.
That might give a little more insight in the School District's choice to have a day off.
"You always want to err on the side of caution," July said. "You have to consider that out in the rural areas kids could be waiting for the bus for five, ten, fifteen minutes. And if they've got any exposed flesh, it certainly could run the risk of frostbite. So no, I'm not surprised."
In temperatures this cold it's probably not a bad idea to have your own cold weather rule.
If you have to be outside, please bundle up.