A winter storm expected to bring heavy snow to Philadelphia on Sunday is already impacting air travel.

The winter storm hitting the tri-state area is significantly affecting air travel, causing cancellations and long delays for flights at John F. Kennedy, LaGuardia, and Newark airports. A handful of flights scheduled to depart the tri-state area have already been canceled,

With a winter storm moving through the tri-state Sunday afternoon, the New York City metro area’s three major airports were all seeing delays and cancellations. As of 2 p.m. Eastern, Newark Liberty International was seeing 254 cancellations into or out of the airport and another 82 delays Sunday,

The entire Delaware Valley will see snow Sunday, with 3-6 inches expected in Philadelphia. On Monday and Tuesday, temps plummet into the teens and single digits.

Heavy snow is expected to blanket large portions of the Eastern U.S. while much of the country will endure dangerously cold temperatures in the coming days

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

Storm Demi is forecast to bring snow to some of the nation’s largest cities, including Washington D.C., New York, and Boston, on Sunday. The winter storm will also usher in cold temperatures in its wake.

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.