The death toll from the fourth nor'easter in three weeks to slam the Northeast stood at four Thursday as millions of Americans dug out and returned to work.

Meanwhile, about 90,000 customers were still without power after the Interstate 95 corridor was pummeled with as much as 19 inches of snow on the first full day of spring.

The fatal car crashes in New York and New Jersey were directly linked to snow, poor visibility and slippery conditions, police said.

The storm created whiteout conditions on Long Island and left parts of New York City under more than a foot of snow — the most the region has seen at this time of year since 1964.

Central Park recorded a snow total of 8.2 inches by 1 a.m. ET Thursday, with 8.7 inches at LaGuardia Airport and 19 inches in the small town of Windber in western Pennsylvania.

New York City schools reopened Thursday, Mayor Bill de Blasio's office said, and the city's subway and NJ Transit were returning to normal. But federal government employees in Washington, D.C., had a two-hour delay and the option for unscheduled leave or telework.

Nearly 230 departures and arrivals were canceled Thursday, including 137 at Newark Liberty airport and 90 at JFK.

Of the customers waiting for the lights to come back on, more than 87,000 were in New Jersey, 3,600 in New York and nearly 3,000 in Delaware.

In Philadelphia, the city's snow emergency was lifted in time for the morning commute, officials said.

In New York, one person was killed after a van carrying five people rolled over on the Wantagh State Parkway, the state police reported. The other passengers were in critical condition, NBC New York reported.

In Newark, Nafis Majette, 32, was killed when the vehicle he was riding in was struck by a stolen Audi, officials said.

Alan Aberden, 26, of East Orange, was charged with aggravated manslaughter, vehicular homicide, leaving the scene of a motor vehicle accident and receiving stolen property, according to the Essex County prosecutor's office.

Photos: 'Tis the season? Spring kicks off with snowy nor'easter

Earlier, New Jersey Gov. Phil Murphy reported that another person was killed when a bus and a vehicle collided on Interstate 78 in Hunterdon County. The New Jersey State Police later said the person — 23-year-old Giovanni Nelson of Allentown, Pennsylvania — was actually in critical condition at a local hospital.

Two other storm-related deaths were reported by police. A 62-year-old woman in the Long Island town of Bellmore died of an apparent heart attack while shoveling snow. And an 87-year-old woman who suffered from dementia was found dead in the snow about a mile from her home in Toms River, New Jersey.

The latest storm was the product of a weather system that had bombarded Texas with hail on Sunday, churned-up tornadoes in Alabama on Monday, and were blamed for severe storms in Florida on Tuesday.

This same system later developed into the nor'easter that blanketed the Atlantic coast from North Carolina to New England in snow, meteorologists said.