The Washington region was blanketed in snow Sunday during the city’s biggest snowstorm in nearly two years, bringing slick roads and a scenic, playful respite from a pandemic.

Two to four inches fell across much of the region Sunday, according to The Washington Post’s Capital Weather Gang. The 2.1 inches that had fallen at Reagan National Airport by evening made it the largest snowfall since Feb. 20, 2019, when 2.6 inches were recorded.

More winter weather is on the way, as Monday was expected to bring occasional mixed precipitation and snow, especially north of the District. By Tuesday morning, the three-day event likely will have dropped two to five inches across the Washington region, falling a bit short of initial expectations, forecasters said.

Snow lovers delighted in the chance to — finally — have some fun in the flakes, especially after months of social distancing to limit the spread of the coronavirus. The Washington D.C. Snowball Fight Association organized a midafternoon winter battle on the National Mall near the Smithsonian Castle, its first such event in two years.

“It’s time to get the gear out of the secret storage and safely enjoy the weather in these weird pandemic times!” organizers wrote in a Facebook post.

The event often occurs at Dupont Circle but was moved to allow for social distancing, organizers wrote. More than 100 mainly 20-somethings, most wearing masks, joined in.

“They’re charging!” one woman shouted, as lines of people ran toward the Capitol, launching snowballs. Another declared it “the most fun I’ve had in weeks.”

Maria Davila, 23, of Springfield, said it was the first time in months she had been around a group of people her age.

“It’s so refreshing to see a bunch of people gathered together after so long,” she said.

Across the region, children giggled under snowflakes while their parents said they were relieved to see some magic back in their lives.

“I feel different today. It feels good,” said Lionel Davis, 42, while walking to Giant in Columbia Heights. “The snow puts me in a happier mood than I’ve been in a while.”

His son, Jacob Davis, 10, packed a snowball in his hands beside him.

“It’s way more snow than I was expecting,” he said.

Jolie Williamson, 3, and her mother, Eva Williamson, 36, brought a pink dream catcher and a bristly tree branch for their snowman at Tubman Elementary School in D.C.

“She’s supposed to bring peace and serenity and unity to D.C.,” Eva Williamson said.

D.C. Del. Eleanor Holmes Norton (D) called on the Capitol Police to allow sledding Sunday and through the week on the Capitol grounds. The popular snow-day destination has been off-limits since after the Jan. 6 attack on the Capitol.

Norton said sledding could be done safely by allowing only children and accompanying adults on the Capitol grounds.

“This could be the only snowstorm D.C. gets this winter and may be one of the best for sledding in years,” Norton said in a statement. “Children and their parents should be able to enjoy sledding on one of the best hills in the city.”

By late Sunday, the hill remained out of reach and empty of its usual sledders and snowmen. The only footprints behind the fence came from the National Guard.

The federal government said late Sunday that its agencies would be open Monday and that employees would have the option of taking unscheduled leave or telework.

The snowstorm delayed the long-awaited start to in-person classes Monday in the District. Thousands of children have been learning on computer screens since March, and the months since have been marked by debates over how to reopen schools safely. But Sunday evening, D.C. Mayor Muriel E. Bowser (D) announced that all Monday classes will be virtual.

Several other school districts across the region announced they were canceling classes or switching to all-virtual classes Monday.

The snow also closed coronavirus testing sites Monday in the region.

With temperatures near freezing most of the day and some roads treacherous, police asked residents to stay home. Many highways in the Washington area were plowed and pretreated, but traffic cameras showed snow piled up on some major arterials and side roads.

Virginia State Police said troopers responded to more than 250 collisions and 230 disabled or stranded vehicles. Metrobus was operating on a “moderate snow plan,” prompting the suspension of some routes and detours of possible hazardous areas.

In Montgomery County, most crashes involved one vehicle — cars into guard rails, jersey barriers and trees — in the southern part of the county on and near the Capital Beltway, said Pete Piringer, spokesman for the county’s fire department. One car went over a guard rail on the Beltway’s Outer Loop and down an embankment near Connecticut Avenue.

Most didn’t result in serious injuries, Piringer said, but single-vehicle collisions usually mean “they’re going too fast.”

In Rockville, a 9-year-old girl suffered a minor elbow injury after her sled hit a piece of equipment plowing a path around Maryvale Park, police said. The girl’s father had stepped in front of a city riding lawn mower that had a small plow attached after seeing her sledding toward it, police spokeswoman Andrea Escher said.

The mower driver stopped before the girl’s sled hit it, Escher said, adding, “She came down too fast and couldn’t maneuver out of the way.”

With bands of snow moving through, crews plowed repeatedly and treated roads to prevent overnight freezing. The expected duration of the storm challenged those working in shifts around-the-clock.

In Maryland, crews that pretreated roads with salt brine overnight Friday took most of Saturday off to rest up for what was expected to be three days of long shifts.

“We want to make sure our crews get the rest they need,” said Sherry Christian, a spokeswoman for the Maryland State Highway Administration.

Jennifer McCord, spokeswoman for the Virginia Department of Transportation, said the agency focused on interstates and primary roads Sunday. It planned to get to neighborhood streets after the heaviest snow stopped, she said.

With wintry conditions expected to change over the next day or two — between snow, sleet and freezing rain — crews would have to alternate between plowing and treating roads with salt and sand.

“The challenge is ensuring we’re keeping up with the changes . . . and battling that refreeze every night,” McCord said.

Washington-area airport officials said runways had been pretreated and were open. But because the storm has affected much of the Northeast, Mid-Atlantic and Midwest, they suggested that travelers check with their airline. before heading to the airport

Jonathan Dean, spokesman for Baltimore-Washington International Marshall Airport, said there might be delays and cancellations possibly into Monday, depending on the track of the storm.

Jason Samenow contributed to this report.