Governors in at least Massachusetts, New Jersey, New York, Philadelphia and Rhode Island have issued states of emergencies, and votes in the House of Representatives were cancelled for Monday night, ahead of impending winter storm Juno, which is expected to dump several feet of snow on seven different states in the Northeast.
Gov. Andrew Cuomo of New York said the subway system will operate on limited service after 8 p.m. on Monday. He said he anticipated closing the Long Island Railroad, Metro-North Railroad and all main roads starting at 11 p.m. The city's zoos and aquarium closed at 3 p.m. on Monday, and the parks and recreational buildings at 6 p.m. All Broadway shows were canceled Monday night. Cuomo told residents to expect power outages.
"This is not a storm to take lightly, and we are taking what we believe are prudent measures," he said during an early Monday afternoon press conference. He will update the state after a 4 p.m. weather advisory update.
New York City Mayor Bill de Blasio canceled school for Tuesday. He ordered all non-emergency vehicles off the roads by 11 p.m. on Monday.
RELATED: Your photos from #Blizzardof2015
Gov. Chris Christie issued a 1 p.m. early dismissal in New Jersey, and cautioned travelers to prepare for rush hour early this afternoon. Public transit will shut down beginning at 10 p.m. on Monday, and state offices will be closed on Tuesday, he added.
"We want to get individuals home and off the roads as soon as possible," Christie said during a press conference. “This is a different kind of storm than we've had before, and it's going to affect our state in different ways."
In Rhode Island, Gov. Gina Raimondo urged residents to prepare their families, homes and elderly neighbors ahead of the storm. Her state, along with Massachusetts, will issue travel bans starting Monday at midnight.
Connecticut Gov. Dannel Malloy issued a statewide travel ban that starts at 9 p.m. on Monday. He has requested out-of-state crews to help with service, and the National Guard and Coast Guard are also prepared to help as needed.
Boston Mayor Marty Walsh canceled school in the city on Tuesday and Wednesday. In Boston, crews stocked plows with salt and sand for clearing snowy, icy roads. Officials warned that heavy and wet snow could trigger power outages.
"Take this very seriously," said Walsh. "Don't wait until the last minute because this storm is giving us a 24-hour head start to get ready for it."
The National Weather Service placed New York City and the surrounding area under a blizzard warning ahead of a "crippling and potentially historic storm" that is bearing down on the nation's largest metropolitan area. The blizzard warning is in effect until 12 a.m. Wednesday, and up to 24 inches of snow is expected.
Millions of people in the Northeast began preparing Monday for the threat of the winter storm. Meteorologists predict that Juno will affect people in at least seven different states, beginning with flurries on Monday that will progress to a heavy snowfall overnight.
The National Weather Service said the storm will impact an estimated 29 million people over a 250-mile stretch in northeastern states, extending from the New Jersey shore to Maine, including the cities of New York, Providence, Hartford and Boston. Meteorologists at The Weather Channel predict more than two feet of snow will fall in some of the cities, including up to 24 inches in Boston, Providence, Rhode Island, and Long Island, New York; 22 inches in Portland, Maine; 20 inches in Hartford, Connecticut; 18 inches in New York City; and 10 inches in Philadelphia.
Meteorologists also expect coastal flooding and damaging wind gusts to possible hurricane strength, up to 70 miles per hour.
By Monday afternoon, airlines canceled more than 6,000 flights through Wednesday, according to FlightAware.
Airlines operating out of Logan International Airport canceled all flights after 7 p.m. on Monday, and they hoped to restart service on Wednesday. Massachusetts Port Authority said officials will only pull the crews off the runway if conditions become too dangerous for employees to continue working.
Amtrak planned to run on a normal schedule on Monday. Metro-North Railroad will run extra afternoon service.
The New York Stock Exchange also operated regularly on Monday, and planned to be open on Tuesday, spokesman Eric Ryan told CNBC. Weather-related market shutdowns historically are rare. The exchange closed for two days after Hurricane Sandy in October 2012.
The one-day snowfall record for New York City is 26.9 inches, which was recorded in Central Park in February 2006. The city was placed under a 35-hour blizzard warning beginning Monday afternoon.
Most schools open on Monday canceled afternoon and evening activities, and some districts in the New York City area planned for early release. Over the weekend and into Monday, grocery stores were packed and many shoppers found empty shelves, as people prepared for the worst from the expected snow accumulation.
"From all the reports I've seen, you all seem to have been to the supermarket in the last 24 hours, and don't know why the rush on bread, but what the heck," Christie said on Monday. "If you want more bread, I'm sure you know, you're able to get it."
NBC News contributed to this report.