Gov. Phil Murphy​ declared a State of Emergency across 21 counties in New Jersey that will be in effect at 8 a.m. Sunday.

With a winter storm moving in, New Jersey is under a State of Emergency Sunday morning. The State of Emergency, declared by Gov. Phil Murphy, went into effect at 8 a.m. Sunday. The state is expecting heavy snow totaling up to 8 inches followed by extremely low temperatures.

The snow started falling in the early afternoon and will become heavier in the early evening, according to the National Weather Service.

An arctic air mass settled over New York City and much of the country Sunday evening, bringing a deep freeze and the chance of more snow than the city has seen in three years.

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

Buckle up for a topsy-turvy weekend of weather – starting with a warm surge and ending with accumulating snow. See that latest projected snow totals and timing of the storm, which will impact Monday morning’s commutes.

The snow from Sunday’s winter storm is starting to pile up in some areas of New Jersey, with as much as a half foot measured on the ground in parts of Morris, Passaic and Sussex counties as of 8 p.m.

A polar vortex is slated to sweep most of the continental US bringing winter storm warnings and a hazardous freeze to millions.

This will be the coldest air of the Winter season thus far, and in many cases the coldest in several years,” the National Weather Service warned.

New York City and the Tri-State area will be digging out Monday morning from the first significant snowstorm of the season, followed by the coldest temperatures in two years over the next few days.