Winter storm updates: Dozens dead across US in wake of massive snowfall, deep freeze

Washington, D.C., has joined 14 states in declaring a state of emergency as the city prepares for ice and the "largest snowfall we've seen in a long time," Mayor Muriel Bowser said Friday.

"Current projections have at least nine inches of snow falling, with the potential for more," Bowser said. "There is a possibility of freezing rain overnight Sunday into Monday, which will increase hazardous conditions."

Bowser said the city is "requesting vehicle support from the D.C. National Guard to ensure our first responders are able to move around."

D.C. public schools were already scheduled to close on Monday for a professional development day for staff.

-ABC News’ Beatrice Peterson

Dangerously cold temperatures are impacting nearly half of the country, including many areas outside of the winter storm. More than 50 million people are on alert for extreme cold, from Minneapolis to Chicago to Dallas to Houston.

The wind chill -- what temperature it feels like – neared minus 40 degrees in Minneapolis and minus 30 degrees in Chicago on Friday morning. In these conditions, it takes as little as 10 minutes for frostbite to develop.

In the South, cities including Dallas, Little Rock, Arkansas, and Memphis, Tennessee, will have bitterly cold temperatures well after this weekend’s storm passes. And since the storm could cause prolonged power outages, people could be left without crucial heating during the arctic blast.

-ABC News’ Kyle David

Ice storms are specifically defined as storms that result in ice accumulations of at least a quarter of an inch on exposed surfaces, according to the National Weather Service.

This system could rival the March 1993 so-called "Storm of the Century," Marshall Shepherd, director of the Atmospheric Sciences Program at the University of Georgia and former president of the American Meteorological Society, told ABC News.

Click here for what you need to know about ice storms.

-ABC News' Julia Jacobo