(CNN) -- How cold is minus 20 degrees really? Cold enough to freeze an egg sunny-side up.
Funda Ray was making breakfast in Hibbing, Minnesota, when she got an idea to demonstrate just how dramatically the temperature had dropped outside.
"I sprayed the cookie pan with Pam and broke an egg on it, and in half an hour, I had a frozen egg," she said. Her husband held up the egg, which she photographed and posted to CNN's iReport.
The coldest weather so far this winter is creeping over the northern United States this week, the National Weather Service said, sending the temperature plunging below zero in Chicago for the first time in 711 days.
Bitterly cold temperatures stretched from the Dakotas to New England, sweeping down into the Ohio Valley. Wind was a major issue in some places, with wind chill warnings and advisories in effect from North Dakota to West Virginia and on into parts of New England.
Residents of Rugby, North Dakota, suffered through wind chills of 51 degrees below zero early Monday morning.
The lowest temperatures were forecast to last into early Thursday.
The cold snap triggered blinding snow in some areas Monday, spawning a number of traffic pileups in Ohio alone, including one fatal wreck involving 86 vehicles. One person died and 20 were taken to hospitals.
Whiteout conditions caused by snow arriving off Lake Erie caused at least three more pileups -- one involving 52 cars, another with 25 vehicles, and a third, in which 23 motorists collided. No one died and no one sustained life-threatening injuries in these accidents, authorities said.
More snow is predicted Tuesday for the eastern shores of Lake Michigan, Lake Erie and Lake Ontario as dry Arctic air absorbs water vapor off the lakes and dumps up to 3 feet of snow in places, forecasters warned,
The cold weather isn't only an annoyance, it can be dangerous.
At 30 below zero Fahrenheit, frostbite can occur in as little as 10 minutes with the slightest winds, and in five minutes in a brisk breeze, the Centers for Disease Control and Prevention warns.
Newborns, the elderly and the homeless can quickly fall victim to hypothermia.
"Cold weather puts an extra strain on the heart," the CDC said, also noting that overexertion can become even more dangerous to those with heart conditions in the Arctic cold.
Locals may be accustomed to winter days when going outside feels like stepping into a deep freezer, but Minnesota resident Patrick -- in a comment on a CNN story -- says it's good to be reminded of the potential dangers.
"This weather is deadly," he wrote, "and last winter didn't even get close to this cold."
His solution to the glacial conditions?
"They should ship us all down to the tropics for the season. It's the most fiscally responsible thing to do."
CNN's Christina Zdanowicz contributed to this report.