However, the U.S. Supreme Court was expected to be open and had arguments scheduled for Monday.
A round of wintry precipitation moved across much of the nation Sunday, bringing a mix of freezing rain and heavy snow to central and eastern states. Authorities warned of possible power outages and flight disruptions from weather that could affect millions.
Ken and Linda Mokry, of Chicago, took advantage of the 54-degree temperature in Washington to visit as many monuments as possible before the storm.
"You've got grass! We don't even have grass to see at home yet," Linda Mokry, 66, said. "We had our first snow right at the end of November ... and we've had snow ever since then, so we've had a long, long winter — way too long."
Ken Mokry noticed the cherry blossom trees are forming tiny buds, making him wish spring would arrive sooner so they could see the trees blossom in pink and white.
"I hope this cold snap doesn't hurt anything," he said. "We were really hoping that we would be able to see them. Maybe next time."
In Pittsburgh, snow began falling about dawn and was expected to taper off before another band of snow hits early Monday. Forecasters were expecting 3 to 6 inches total. Philadelphia was expected to get four to 8 inches through Monday. More than 6 inches would make it the city's second snowiest winter, surpassing 65.5 inches that fell in 1995-96.
Nearly 1,900 flights in the United States were canceled and another 1,863 delayed Sunday evening, according to flight tracking site FlightAware.com. The bulk of the problems were in Dallas, Chicago and Newark, N.J. There are more than 30,000 flights in the United States on a typical day.
Another 1,612 flights for Monday were also already canceled, with Washington's Regan National airport accounting for 246 of them.