Highways are being closed, flights cancelled, mass transit delayed.
Here's what's happening in the air and on the ground:
New York
In New York City, express service on subway lines has been shut down, and buses are running with delays.
Metro-North commuter trains will run only hourly after 8 p.m. on all three lines, and Long Island Rail Road trains are running with slight delays on the Ronkonkoma branch.
Alternate side parking rules in the city have been suspended for Friday, but parking meters will be enforced.
Citi Bike has not been shut down, but the re-installation of some Times Square stations removed for New Year's Eve celebrations has been delayed to next week.
After midnight, several major highways will be shut down: the Long Island Expressway in Nassau and Suffolk counties, I-87 from NYC to Albany, and I-84 from the Connecticut state line to the Pennsylvania state line. They will reopen at 5 a.m., weather permitting.
Local airports are staying open, but are experiencing delays, especially Newark.
Boston
Logan Airport said on Facebook it will remain open overnight, but expects its last departure to be around 8:30 p.m., and flights to resume late Friday morning.
The Red, Blue, Orange, and Green metro lines may run with delays, and the Mattapan Trolley line may use alternate shuttle buses.
Pennsylvania
The speed limit has been dropped to 45 mph on several highways, including all of I-81, I-80, I-84, and I-99.
Flights are being delayed by an average of 26 minutes at Philadelphia International Airport. 19% of departing flights and 10% of inbound flights have been cancelled.