The worst of the nor'easter that slammed the Northeast with record snowfall has passed, but 'dangerously cold' wind chills remain in some areas

The worst of the nor'easter that dumped record snowfall in parts of the East Coast has passed, but "dangerously cold" wind chills were set to stick around in some areas Sunday morning, forecasters said.

Roughly one million people across the Northeast were under winter weather alerts early Sunday, down from the nearly 16 million who were affected by such alerts Saturday night.

Live updates: Nor'easter slams the Northeast

"That is a huge drop-off as the storm exits the most populous areas of the eastern seaboard," CNN meteorologist Derek Van Dam said.

Blizzard warnings -- which affected millions across multiple states Saturday -- have also been scaled down to eastern and northern Maine, where more than 240,000 people were affected as of 1 a.m. Sunday, according to the National Weather Service (NWS).

A blizzard, as defined by the NWS, requires blowing or falling snow, winds of at least 35 miles per hour, and visibility of a quarter mile or less for at least three hours.

Those conditions were reached Saturday in several locations across Rhode Island and eastern Massachusetts, including Boston, the NWS said.

Wind speed -- which reached more than 80 mph Saturday across eastern Massachusetts -- is expected to ease to about 15-25 mph Sunday, though gusts could be higher in some local areas, according to Van Dam.

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Still, much of the Northeast can expect "dangerous" wind chills, some dipping below zero Sunday morning as the storm exits the region, the NWS warned. More than 760,000 people from parts of western Virginia through Maine are under those warnings effective until 7 a.m. in some areas and 10 a.m. in others.

Later Sunday, some areas including Buffalo, New York, and Pittsburgh will see temperatures improve by roughly 10 degrees.

Meanwhile, cities including New York, Boston and Philadelphia will see a slight dip of about 4 degrees Sunday.

"Although temperatures are going to rebound (Sunday), we will have to be patient for any real warm up, which doesn't come until the middle of the week," Van Dam said.

How strong a blizzard's impact may be 01:20

The frigid cold follows dense snowfall that broke records throughout the Northeast in parts of southern New Jersey, New York, Pennsylvania and Massachusetts.

The storm became a "bomb cyclone" Saturday morning, meaning it strengthened rapidly and had the barometric pressure drop more than 24 millibars within 24 hours, the Weather Prediction Center said.

The storm wreaked havoc on transportation in the region, creating dangerous conditions on roadways and delays and cancellations on air and rail travel.

More than 3,580 flights within, into or out of the US were canceled Saturday, according to FlightAware, and more than a thousand were already canceled for Sunday as of the early morning. Major airlines offered waivers and alternative options to passengers whose travel was affected by the storm.

Record snow and roaring winds

The bomb cyclone brought heavy snow that accumulated quickly as howling winds blew through the region.

The town of Stoughton, Massachusetts, recorded a staggering 30.9 inches of snowfall by Saturday night, the NWS said. And winds in parts of Barnstable County, Massachusetts, where Cape Cod is located, reached 81 mph Saturday, the service said.

By Sunday morning, up to 2 feet of snow could fall from Long Island through Rhode Island, Massachusetts, New Hampshire and Maine, CNN forecasters said.

An aerial view shows snow cover in Central Park Saturday.

Here are some notable snowfall records:

• Atlantic City, New Jersey: The city crushed its all-time January snowfall record by Saturday, reaching a monthly total of 33.2 inches of snow. The prior monthly record of 20.3 inches was set in January 1987. The city's 14 inches of snow Saturday also beat its previous record for the calendar date, which was set in 2014 at 7.3 inches.
• Boston: Logan International Airport tallied at least 23.6 inches of snow by Saturday night, said the NWS, making Saturday the snowiest January day Boston has recorded and tying the record for biggest 1-day snowfall total. The previous record was set on January 27.
• Central Park, New York: The iconic park saw 7.3 inches on Saturday, beating the previous record for January 29 of 4.7 inches set in 1904.
• Philadelphia: The city was hit with 5.8 inches of snow Saturday, beating the previous calendar day record of 5 inches set on January 29, 1904.