The National Weather Service issued a winter storm advisory until 1 p.m. in New York City. The area got 1 to 2 inches of snow and sleet by early morning. It was to be followed by an inch of ice before turning to all rain by late morning.
Hundreds of schools up and down the East Coast were closed or having delayed starts, including the Washington, D.C. area, eastern New York and southern Vermont.
In New Jersey, Newark Liberty International Airport was open but the airport's largest airline, Continental, said it halted its flights there because of freezing rain and snow.
Speed limits were lowered on highways from Delaware to New Jersey.
Dozens of collisions were reported in Connecticut, including a crash between a southbound Amtrak train and a FedEx truck that became stuck at a Wallingford crossing.
Wallingford fire officials said none of the train's 90 passengers were injured, and the truck's driver was already out before the slow-moving train hit.
The eastern half of New York was expected to get up to 8 inches of snow, along with freezing rain and sleet. Coastal New Hampshire was bracing for power outages as ice was expected to build up on power lines later Tuesday.
Rail service was also affected due to ice. Metro-North Railroad, which serves commuters from Connecticut into New York City, reported up to 40-minute delays on some lines. The Southeastern Pennsylvania Transportation Authority, which serves the Philadelphia area, reported delays on its commuter rail service and bus detours.
The MTA reported no major problems, but some trains ran on modified schedules.
Meanwhile, frigid temperatures are on tap overnight, with a low around 20 degrees, but the afternoon will turn significantly warmer -- around 40 degrees. Rain is in the mix through Wednesday morning.
Today's wintry mix marks the fourth snow storm of the season. Snow from the after Christmas blizzard is still on the ground around the region, unable to melt as temperatures remain around the freezing mark.
After a brief warm-up to around 40 degrees on Tuesday and Wednesday, the end of the week will again turn very cold, with highs around 28 degrees on Thursday and Friday -- and, much to the dismay of weary tri-state residents, possibly some more of the white stuff.
After a Christmas weekend blizzard dumped 20 inches of snow on New York City, Mayor Michael Bloomberg was criticized for the slow cleanup. Up to 12 inches of snow blanketed the area again last week, but the city was prepared and the streets were quickly plowed.
As always, check back with NBCNewYork.com for up-to-the-minute weather information and the latest on forecasts, school closings and transit alerts.