The National Weather Service issued a winter storm warning for the area until 4pm ET. Wind gusts of up to 35mph were forecast and travel was expected to be very difficult, the weather service said.

“The timing of this isn’t great,” said NWS meteorologist David Roth. “For the DC area, it’s morning rush hour. At least for places to the north-east, it’ll be closer to midday.”

More than half flights were delayed or cancelled at Ronald Reagan national airport, Baltimore/Washington international airport and Washington Dulles international airport, according to FlightAware.com. A quarter of the flights at New York’s three major airports were off.

The Weather Prediction Center said 2in of snow per hour could fall in some areas, and thunder snow was possible. Localized snowfall totals could reach 10in

Snow began falling on Sunday night in parts of Alabama, Kentucky and Tennessee. A winter storm warning was issued in parts of northern Alabama and southern Tennessee and portions of Georgia, Kentucky, North Carolina and West Virginia. By early Monday, more than 400,000 customers were without power in Tennessee, Georgia, the Carolinas and Virginia.

Impacts from the winter storm were expected across the south, Appalachian states, the mid-Atlantic and up the east coast.

In Washington, the US Office of Personnel Management announced that federal offices would be closed. Emergency employees and telework employees were expected to keep working, the OPM said.

Many Covid testing and vaccination sites were closed in Virginia and in Maryland due to the weather. Multiple school districts in the region said they would be closed, delayed or have virtual learning Monday. DC Public Schools said students and staff wouldn’t be returning to school until Thursday.