Snow was falling in the Mid-Atlantic and New York City on Sunday. The coldest air in several years will descend across much of the country starting Monday, forecasters said.

"The level and extensiveness of the frigid air may be tough to match the rest of the winter," forecasters warned.

Extreme cold could expose residents of several states to conditions like hypothermia and frostbite over the weekend.

A potent surge of Arctic air starts settling in Monday evening as a massive dip in the jet stream pulls in frigid air across the entire eastern half of the country. Temperatures are set to drop as low as 20 degrees below average through Thursday with the highs only reaching the teens and some lows even plunging below zero.

Light snow flurries in Indianapolis early Sunday signaled an approaching arctic air mass that could bring dangerous wind chills as low as -20 degrees across Indiana in the coming days. Bitterly cold temperatures are forecast across Indiana from 7 p.