(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.
This morning on "Early Start," meteorologist Jennifer Delgado reports on the latest temperatures and wind chills across the U.S., and what you can do to stay warm.