Powerful nor'easter slams East Coast, with heavy snow and strong winds

Millions of Americans are under winter weather alerts Saturday as a nor'easter slams the Northeast.

Whiteout conditions persist as the winter storm makes its way toward the New England coast.

Snow has been falling at a rate of 2 to 4 inches per hour in Massachusetts, Gov. Charlie Baker said during a Saturday evening press briefing. The winter storm is "delivering as expected," he said, with strong winds and large amounts of snow hitting the state's eastern, southeastern and coastal communities the hardest.

Parts of New Jersey, including Atlantic City, saw snowfall rates upward of 2 inches per hour, while eastern Connecticut saw as much as 3 inches per hour.

In addition to the snowfall, strong wind gusts of 60 to 70 mph have been reported along the Northeast coastline.

States of emergency were in effect in several states as they braced for the worst of the storm system Saturday afternoon.

Whipping winds, treacherous travel, potential power outages and frigid temperatures are all concerns associated with the winter nor'easter. Over 100,000 customers are without power in Massachusetts, and over 3,550 flights have been canceled within, into, and out of the U.S. Saturday, according to Flightaware.

In Connecticut, airports are "down at this point," Gov. Ned Lamont said during a briefing midday Saturday. Metro-North is running on limited hourly service, and Amtrak is not operating, officials said.

Snow totals, treacherous conditions

By Saturday afternoon, over a foot of snow had so far fallen along the Northeast coast, with parts of New Jersey and Long Island reporting over 18 inches.

Additional snow accumulations of 3 to 6 inches are forecast from eastern Long Island up into central New England, while another 6 to 12 inches is expected along the New England coast.

Parts of Connecticut to Maine may see up to 18 to 24 inches of snow total, with the possibility of up to 24 inches near Boston Metro -- a potential record breaker. For the city of Boston, the most snowfall in one day in January on record is 22.1 inches -- Jan. 27, 2015 -- and the most snowfall in one day on record overall is 23.6 inches, which happened Feb. 17, 2003.

Southeastern Massachusetts could get about 30 inches of snow, the governor said.

Coastal New Jersey; Suffolk County, New York; Rhode Island and coastal Massachusetts experienced whiteout conditions -- persistent heavy snow and gusty winds.

The Interstate 95 corridor north of New York City toward Boston and Portland, Maine, saw whipping wind gusts of 45 mph to 70 mph.

Below-zero wind chills

Parts of the Great Lakes and New England likely will experience bitterly cold temperatures with wind chills near 25 below zero.

The Northeast will feel frigid Saturday night as wind chills plunge to 2 and 5 below zero in New York City and Boston, respectively.

Cold weather is even heading south to Florida with temperatures dipping into the upper 20s by early Sunday. Wind chill alerts have been posted for cities including Miami, Naples and West Palm Beach. Freeze warnings were in effect for much of Florida Saturday night.

Coastal concerns

There are coastal concerns about storm surge and tidal influence especially along the coastal towns in Suffolk County, New York, which could see 4- to 8-foot-high waves during high tide Saturday night and into Sunday.

Boston may also get battered with largest wave swells at 15 to 20 feet.

Beach erosion, localized flooding and property damage are all possible in these areas with the storm and high tides.

Some coastal communities in Massachusetts are experiencing minor to moderate flooding, Lt. Gov. Karyn Polito told reporters Saturday. Nantucket saw high floodwater, with "significant flooding" downtown, officials warned.

However, there is one silver lining to this winter storm: The storm system remained easterly, meaning less heavy snow and weather-related snarls for states west of I-95.

ABC News' Victoria Arancio, Daniel Peck, Hilda Estevez and Ahmad Hemingway contributed to this report.