Millions of people in New York City and a large swath of the northeastern U.S. are stuck at home under road travel bans and blizzard warnings Monday as heavy snow and strong winds intensified, creating whiteout conditions in the densely populated region.

Snow fell at a rate of 2 to 3 inches (5 to 7.6 centimeters) an hour early Monday from New York through Massachusetts. Some areas have gotten well over a foot (30 centimeters) of snow since Sunday, along with wind gusts of over 30 mph (48 kph) and low visibility.

More than 5,000 flights in and out of the U.S. were canceled for Monday, according to the flight tracking website FlightAware. Most were canceled in New York, New Jersey and Boston.

Here's the latest:

New Jersey speed limits lowered

Speed limits on New Jersey interstates and state highways have been lowered temporarily to 35 mph (56.3 kph) under an emergency traffic regulation order.

The order started Sunday afternoon and includes the New Jersey Turnpike, Garden State Parkway and Atlantic City Expressway.

Public transit delays in New York

The Metropolitan Transportation Authority in New York City says some express trains are running local on Monday and riders should expect delays. Some delays could be severe, especially on lines running above ground.

Bus riders also should expect longer waits as articulated buses have been removed from service during the storm.

Meanwhile, Long Island Rail Road service has been fully suspended until further notice, while the Metro-North Railroad is operating on a reduced schedule in some areas.

Staying safe from winter weather dangers

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What’s a bomb cyclone?

The weather service referred to the storm as a “classic bomb cyclone/nor’easter off the Northeast coast.” But what does that mean?

According to the U.S. National Oceanic and Atmospheric Administration, certain storms undergo bombogenesis, which happens when a storm’s central pressure drops at least 24 millibars in 24 hours. These storms are sometimes called bomb cyclones. Storm intensity is measured by central pressure, so the lower the pressure, the stronger the storm.

Such rapidly strengthening storms can produce heavy rain, blizzard conditions and intense winds that can lead to downed trees and power outages.

Bomb cyclones can occur in any season, but primarily develop during fall and winter when frigid air from the Arctic can creep south and clash with warmer air masses.

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Travel impacts

More than 5,000 flights in and out of the United States were canceled for Monday, according to the flight tracking website FlightAware. Most were canceled in New York, New Jersey and Boston.

Public transit also was suspended in some areas. And DoorDash announced it was suspending deliveries in New York City overnight.

“The combination of heavy snowfall and strong winds will continue to produce blizzard conditions along the Northeastern Seaboard,” the weather service said Monday. “Sharply reduced visibility will make travel extremely treacherous across these areas.”

Millions are stuck at home

Heavy snow and strong winds have intensified, creating whiteout conditions in a large swath of the northeastern U.S.

The National Weather Service called travel conditions “nearly impossible.”

Blizzard warnings stretched from Maryland to Maine. Cellphones across New York City received wailing push alerts Sunday night announcing a ban on non-emergency travel on all streets through noon Monday because of “dangerous blizzard conditions.” Rhode Island and New Jersey implemented similar restrictions.

Reported snowfall

22.5 inches (57 centimeters) at New York, Long Island MacArthur Airport

About 15 inches (38 centimeters) fell in New York City’s Central Park

About 18 inches (46 centimeters) in Newark, New Jersey

17 inches (43 centimeters) in New London, Connecticut

17 inches (43 centimeters) in North Kingstown, Rhode Island