(ABC News)--Snow began to blanket cities across the Northeast on Tuesday in what could turn out to be one of the most severe blizzards of the year.
Blizzard warnings have been issued in parts of 8 states in the densely populated Northeast, causing thousands of school cancellations and halting work and travel for millions of Americans.
"A very strong winter storm could be life threatening for those who do not pay attention to safety precautions," the National Weather Service warned late Monday.
Major cities from Philadelphia to Boston could get between 10 and 20 inches of snow, forecasters said.
The storm is set to bring heavy snow and strong winds that could make travel “nearly impossible in many areas,” according to the NWS.
Parts of Pennsylvania, New Jersey, New York, Connecticut, Rhode Island, Massachusetts, New Hampshire and Maine are under blizzard warnings.
Nearly 6,000 flights scheduled for Tuesday were canceled, while an additional 690 were delayed, according to the Houston, TX-based aviation site FlightAware.
Nearly half of the cancellations, about 2,580, were at three airports in the New York City metro area: John F. Kennedy, LaGuardia, and Newark Liberty.
As of 2:30 a.m. ET, 2,932 schools across the Mid-Atlantic and Northeast corridor were scheduled to close or have delayed opening on Tuesday. Schools in New Hampshire and Massachusetts were impacted the most, with 914 and 630 closings or delays scheduled, respectively.
Heavy snow is expected to accumulate quickly, with some areas forecast to see between 2 and 4 inches of snowfall per hour during Tuesday afternoon.
Wind gusts of up to 55 mph could add to the storm's impact.
The snow is expected to make many roads impassable and could produce widespread power outages due to the weight of the snow on tree limbs and power lines, the NWS said.
The service warned people in the affected areas to stay inside.
“Visibilities will become poor with whiteout conditions at times. Those venturing outdoors may become lost or disoriented,” the NWS said in a statement early Tuesday. “So persons in the warning area are strongly advised to stay indoors.”
The storm comes just days before the official start of Spring on March 20, in a region where many welcomed celebrating springlike temperatures just days ago.
The weather system dumped a swath of snow on parts of the Midwest before moving east across the country on Monday.
Icy road conditions in Chicago, Illinois, led to two car wrecks early Tuesday that involved 34 vehicles.
Seven people were transported to local hospitals with minor injuries as a part of those incidents, which occurred on the Kennedy Expressway, officials said.
Separately, four men died while removing snow in southeast Wisconsin, where snowfall topped 12 inches in some areas. The men were all between the ages of 64 and 76, according to ABC News affiliate WISN.