New York Mayor Zohran Mamdani on Sunday ordered the city’s transit system to shut down except for emergency travel as a major snowstorm began sweeping across the U.S. Northeast.

Tens of millions of Americans from Washington, D.C., to the state of Maine were bracing for the storm, with snowfall expected to reach up to 60 centimetres (24 inches) in some areas.

The National Weather Service warned that a powerful winter storm would hit a region stretching from Maryland to southeastern New England, making travel “extremely dangerous.”

At the height of the storm, snowfall rates could reach between five and eight centimetres (2 to 3 inches) per hour, the agency said.