Thousands of marching soldiers. Dozens of helicopters flying overhead. Hundreds of military vehicles, including 28 tanks. These will all parade through the heart of D.C. for a celebration honoring the 250th birthday of the U.S. Army on Saturday — also President Donald Trump’s 79th birthday.

It is expected to be the largest military parade in the nation’s capital since the end of the first Gulf War in 1991 and will be part of a day-long extravaganza on the National Mall that will include musical performances, parachutists and fireworks.

There will be street closures, heightened security and protests, too. Here’s what you need to know.

Activities are planned throughout Saturday. Here’s a breakdown.

8:15 a.m. Wreath laying at the Tomb of the Unknowns at Arlington National Cemetery, Virginia; open to the public and live-streamed.

9:30 a.m. – 12:30 p.m. Fitness competition on the National Mall.

11 a.m. – 6 p.m. Army Birthday Festival on the National Mall, including military demonstrations, equipment displays, live music and food trucks.

6:30 p.m. The parade route runs along Constitution Avenue NW, beginning at 23rd Street near the Lincoln Memorial and finishing about a mile down the road, at 15th Street near the Washington Monument. The parade involves thousands of soldiers in historic and modern uniforms, dozens of Army vehicles including Abrams tanks, a flyover and a parachute jump.

9:45 p.m. Fireworks on the National Mall.

According to the Pentagon, about 150 ground vehicles, 6,600 soldiers and 50 aircraft will appear in the parade, grouped to represent each major era of the Army’s history.

Roads will be closed to vehicles roughly between Seventh Street NW and the Potomac and from E Street down to Independence Avenue. That includes the entire area encompassing Lafayette Square, the White House, the Ellipse, the Washington Monument, the Vietnam Memorial, the Lincoln Memorial and West Potomac Park.

The 12th Street Expressway and the Constitution Avenue entrance to the Ninth Street Expressway are covered by the closures. A broader swath of downtown will be limited by police to drivers who need to get to a location in the area: south of E Street to Fourth Street NW on the east side of the White House, and south of H Street until 23rd Street on the west side.

While the Jefferson Memorial and Hains Point are open to pedestrians from the D.C. side, the roads there are blocked off. Access to Virginia around and over the Arlington Memorial Bridge will be blocked. Rock Creek Parkway south of Virginia Avenue is closed, and on the other side of the bridge the George Washington Memorial Parkway is closed in both directions between I-395 and Arlington Boulevard. (Unrelated construction will also require detours on the parkway farther north at Route 123.)

Other roads between D.C. and Virginia are open, but exits around the Mall are closed.

See the full list of street closures and parking restrictions affecting D.C. and Northern Virginia, which are subject to change and may be updated before Saturday, here. Closures apply to parking, too.

Boats and paddleboards will not be allowed between the 14th Street Bridge and the Theodore Roosevelt Bridge, including in the Tidal Basin.

The Smithsonian station entrance on the Mall will be closed, but otherwise Metro is running as normal. Buses that travel through the blocked-off areas of downtown D.C. and Northern Virginia — 3F, 3Y, 11Y, 16E, 31, 32, 36, 42, 43, 52, 59, 63, 64, 70, 74, 79, N2, N4, P6, S2 — will face detours and delays from 11 p.m. Thursday to 7 a.m. Monday.

Flights in and out of Reagan National Airport will be halted for the military flyovers between 6 p.m. and 9:30 p.m. Saturday, the Federal Aviation Administration said. The airport will be open, but flights in and out — about 65 arrivals and 35 departures — will be delayed for an average of about three hours, until after the event.

Yes. To attend the morning festival, evening parade or both, you must enter through designated screening checkpoints.

The checkpoint to enter the festival opens to the public at 8 a.m. It is on the east side of the National Mall at Seventh Street NW, between Madison Avenue NW and Jefferson Drive SW. There are two checkpoints to enter the viewing area for the parade that open to the public at 2 p.m. These checkpoints are at 14th Street NW between Constitution Avenue NW and Independence Avenue SW, and at C Street NW between 18th Street and 19th Street NW.

Expect to encounter a robust security perimeter that includes 18.5 miles of steel fencing and 175 metal detectors.

Pedestrians not planning to attend will be able to access the Mall, but the White House and parkland to its west will require going through security. The Mount Vernon Trail will be closed to pedestrians and cyclists between the 14th Street Bridge and the Memorial Bridge, and the path along Rock Creek Parkway will also be closed to pedestrians and cyclists below Virginia Avenue.

After entering through the parade checkpoint, spectators will be able to stand along the parade route on Constitution Avenue NW. The event is standing room only — no bleachers or seating available, according to the Secret Service. Most people viewing the parade will be directed to the south side of Constitution Avenue NW, though some space will be available on the north side of the street. Officials say the space can accommodate “hundreds of thousands” of people.

Those who exit the parade viewing area will need to go through a checkpoint again before reentering.

Yes, many items are banned from both the festival and the parade grounds. Among the prohibited items: umbrellas with metal tips (those without metal tips will be permitted); balloons; folding chairs; bags larger than 18 x 13 x 7 inches; signs larger than 20 inches x 3 feet x ¼ inch; and glass, thermal or metal containers.

Officials have said they are preparing for “hundreds of thousands” of people to attend Saturday’s events, but they have not responded to requests about what that number is based on.

According to The Washington Post’s Capital Weather Gang, a slow-moving front approaching D.C. from the north could trigger heavy showers and storms, including lightning. The potential showers are most probable in the late afternoon and evening, though it is likely the morning and early afternoon will be mostly dry.

As for the temperature, forecast models project highs in the low 80s and near 90, depending on cloud cover. Confidence is high that it will be humid, which will make it feel several degrees hotter; hydration will be key for those planning to spend long hours outdoors.

Because of the large crowds, noise and the weather forecast, Secret Service officials are asking people to leave pets and emotional support animals at home for their safety. Service animals are welcome.

Possibly. District leaders have expressed concern about potential damage to city roads, though the Army has said it would pay for any repairs. Security officials said at a recent briefing that they expect to execute the parade with “little to no damage” to the city’s streets because of safety precautions that include metal plating on areas where tanks have to steer sharply and matting where vehicles are staged.

Tanks that will be used during the parade have been fitted with rubber trackpads that will lessen impact to the roads, said Col. Jesse Curry, a member of the U.S. Army Corps of Engineers. Curry said Army engineers worked with National Park Service and Federal Highway Administration officials to assess the impact of tanks and other vehicles on the roads and come up with a plan to protect them.

“Throughout the straightaways, we really have very little or no concerns that there would be any other damage,” he said. “The plates, where we’re putting them, are designed to minimize or eliminate all possible damage.”

More than 1,600 rallies are planned across all 50 states as part of the No Kings movement organized by a coalition of organizations calling for a “nationwide day of defiance.” A full list of locations can be found on the group’s website. There are No Kings events in Virginia and Maryland, but not in Washington. The flagship march and rally will be in Philadelphia, with organizers aiming to “draw a clear contrast between our people-powered movement and the costly, wasteful, and un-American birthday parade in Washington.”

Within the city, local group Free DC is hosting a “DC Joy Day” at Anacostia Park on Saturday from 3 to 8 p.m. celebrating the city’s “people, culture, and our connections to one another,” according to its website. Organizers say there will be face painting, line dancing, lawn games and free food on the grill for the first 500 people. There will be a free shuttle from Anacostia Metro to Anacostia Park Field 7, every 30 minutes between 3 and 8 p.m., and DC Queer Bikes and Hill Family Biking will meet at Nationals Park at 2 p.m. for a group bike ride to the event.

Trump said Tuesday that protesters who assembled during a military parade would be met with “very big force.”

previous coverage

• Soldiers rehearse, prepare armored vehicles for Army’s 250th birthday parade
• Army parade tanks will be a 70-ton test for DC streets
• Tanks and soldiers are coming to DC for the parade, and so is this dog
• Tanks, heavy vehicles on way to Washington as Army prepares for 250th anniversary celebration