WASHINGTON >> The first major winter storm of the new year pummeled the U.S. Mid-Atlantic states today, closing federal offices and public schools in Washington, D.C., after dumping 12 inches of snow on parts of the Ohio Valley and Central Plains.

According to the US National Weather Service, more than five inches had fallen in the nation’s capital as of midday today, with as much as 12 inches falling in some surrounding areas of Maryland and Virginia. Snow was forecast to continue before the system moves offshore this evening.

Significant traffic delays were expected along the storm’s route and officials urged motorists to stay off the roads if possible. Governors of several states, including Kansas, Kentucky, Arkansas, West Virginia, Virginia and Maryland, have declared states of emergency.

After the storm, dangerously cold Arctic air filled the void, bringing freezing rain and icy conditions to a swath of the country stretching from Illinois to the Atlantic coast. Unseasonably cold temperatures are expected to continue for the rest of the week.

The Central Plains, where the storm dumped heavy snow over the weekend, was already frozen. Parts of Kansas experienced bitter wind chills overnight, with temperatures ranging from 5 to nearly 25 degrees Fahrenheit below zero (minus 15 to 32 degrees Celsius). The cold air will persist and daytime highs will only be in the mid to low 20s.

The airport in Kansas City recorded 11 inches (28 cm) of snowfall, the most of any severe weather event in more than 30 years, the National Weather Service said. Missouri State Police said they responded to more than 1,000 stranded motorists and 356 crashes Sunday, including one fatality.

In Washington, Congress met during the storm to officially confirm the election of Republican Donald Trump as president. But federal offices in the nation’s capital were closed.

In the city’s Meridian Hill Park, hundreds gathered for a massive snowball fight organized by the so-called Washington DC Snowball Fight Association. The fighters – many wearing ski goggles for protection – fired volleys of frozen projectiles as a dog tried to catch the ammunition in its mouth.

“I didn’t come here to make friends!” Jack Pitsor, who lives across the street from the park, shouted with a laugh before hurling a snowball toward enemy lines.

School districts in numerous states were closed today due to the storm, including public schools in Indianapolis, Cincinnati, Washington and Philadelphia.

The storm also left more than 330,000 homes and businesses without power in the central and southern United States today, data from PowerOutage.us showed.

According to tracking service FlightAware.com, nearly 1,900 flights within, to and from the United States had been canceled as of 1:30 p.m. EST (1830 GMT). Amtrak has canceled dozens of trains on the busy Northeast Corridor line between Boston and Washington.

The three D.C. area airports — Reagan National, Baltimore/Washington International and Dulles — were all open and crews were working to clear snow from airfields, but many flights were delayed or canceled.

Virginia State Police responded to 300 car crashes between midnight and 11 a.m., while Maryland State Police received 123 crash reports between 1 a.m. and 11 a.m., spokespeople for the two agencies said. A man died in southeastern Virginia after losing control of his pickup truck around midnight, with police citing both alcohol and the weather as factors, local media reported.