Coldest week of the winter for northern United States

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.

http://www.cnn.com/2013/01/22/us/weather/index.html?hpt=hp_inthenews