Millions of Americans are getting ready to emerge from coronavirus lockdowns and venture outdoors to celebrate Memorial Day weekend at beaches, cookouts and family outings, raising concern among public health officials that large gatherings could cause outbreaks to come roaring back.

Medical experts warn that the virus won’t take a holiday for the unofficial start of summer. The Centers for Disease Control and Prevention recommends that people stay home, avoid crowds and connect with family and friends by phone or video chat.

Dr. Seth Cohen, an infectious disease expert at the University of Washington Medical Center-Northwest in Seattle, advised that people keep their distance, wear masks and avoid sharing food and drinks.

“Punch bowls. Nachos. These things are a no-no,” Cohen said.

Dr. Deborah Birx, coordinator of the White House coronavirus task force, said today that people can enjoy the outdoors if they stay at least 6 feet (2 meters) apart. Birx suggested playing tennis with marked balls, one for each player to handle, or not touching flags on the golf course.

“That is your space, and that’s the space that you need to protect and ensure that you’re social distanced for others,” Birx said at a White House briefing. She also suggested disposable utensils for picnics and potlucks.

Birx said COVID-19 is declining nationwide, but many healthy-seeming people are unknowingly infected, making social distancing, face coverings and frequent hand-washing necessary.

The holiday, which honors fallen service members, arrives amid the bleakest economy in decades. Tens of millions have been laid off since the virus hit hard in March and forced shutdowns. Unemployment has reached its highest level since the Great Depression. Federal Reserve Chair Jerome Powell warned Thursday that prospects for a recovery will remain unclear until the health crisis is resolved.

Many Memorial Day commemorations have been canceled or downsized, including concerts and fireworks shows. Parks, beaches, campgrounds and swimming pools remain closed in much of the country.

But plenty of popular spaces will be open — with limits.

Californians headed into the weekend with both excitement and anxiety after restrictions eased in many areas. The nation’s most populous state has started seeing a decline in COVID-19 hospitalizations after being the first to order a statewide shutdown.

David Spatafore, who owns Blue Bridge Hospitality restaurant group, was looking forward to today’s reopening of patio seating at the group’s pizzerias and dining rooms at its high-end steakhouse in Coronado, across the bay from San Diego.

“I think people are going to be so happy to be able to go back out and not eat out of a plastic container or cardboard box,” he said. “I know I am.”

In Virginia Beach, Virginia, the famed 40-block boardwalk and sandy shoreline reopened, but with spacing guidelines and groups limited to 10. Group sports such as volleyball are prohibited, along with tents and alcohol.

Mayor Bobby Dyer said about 150 “beach ambassadors” in red shirts will “diplomatically” ask people to follow rules.

Without clear federal guidance, state and local officials have been left to figure out how to celebrate the holiday safely. Social distancing and bans on mass gatherings remain in place throughout much of the country.

Keeping holidays safe is a challenge worldwide. On the same weekend as Memorial Day, the Muslim world will mark the fast-breaking festival Eid al-Fitr. On Monday, residents in the United Kingdom get a bank holiday.

Dr. William Schaffner, an infectious diseases expert at Vanderbilt University, warned that being on holiday can lead some people to drop their guard.

“They forget to wear masks,” Schaffner said. “They’re not so keen on 6-foot distancing.”

Jersey Shore beaches will be open but there will be no fireworks, Ferris wheel rides, roller coasters, go-karts or arcade games. Atlantic City’s casinos remain closed.

Some locals plan to sit this summer out.

“The unfortunate thing is that all the out-of-town people have been cooped up the same amount of time that the locals have been here,” said Christine Barthelme of Point Pleasant, New Jersey. “My family will do mostly what we do on every holiday weekend here: relax in our backyard, have a barbecue and light the fire pit.”

Beaches, hotels and restaurants remain largely shut down in South Florida. The Urban Beach Week festival, which annually draws tens of thousands to Miami Beach for hip-hop and reggae shows, was called off.

“We saw what happened in early March with spring break crowds,” Miami Beach Mayor Dan Gelber said, recalling the raucous scenes of youngsters partying in close quarters.

But up the coast in Palm Beach County, officials were preparing for beachgoers.

“Lifeguards and other parks staff will be monitoring the beaches and reminding park users to practice social distancing,” said Chris Korbelak, public engagement manager for the county parks department.

Theme parks are closed at Walt Disney World and Universal Orlando, but both have reopened their entertainment and restaurant complexes, where guests can expect mandatory masks, hand-sanitizing stations and other measures.

For the hard-hit tourism and hospitality industry, there is modest hope Memorial Day will mark the start of something resembling recovery.

“This weekend is an early indicator as to how consumers feel about coming back and partaking in normal social behavior,” said Jason Guggenheim of Boston Consulting Group, which has surveyed consumers.

Data and consulting firm Tourism Economics projects travelers will spend $4.2 billion on Memorial Day weekend, compared with $12.3 billion last year.

Airlines, meanwhile, have largely written off hope of a quick rebound. Air travel in the U.S. remains down about 90% from a year ago, according to Transportation Security Administration figures.

Oklahoma resident Seth Rott this week boarded a plane for the first time since the pandemic to visit a friend in Washington for Memorial Day. Rott said he had little concern about social distancing or safety, given airlines’ anti-virus measures.

“I think it will probably be the easiest flight that I’ve ever had just because of a lack of traffic,” he said.

But for most who leave home, it will be by automobile and for relatively short excursions to places like Washington state’s Mt. Baker-Snoqualmie National Forest.

“We’re expecting a bottleneck at some of the popular trails,” spokesman Colton Whitworth said, “especially the lower-elevation ones closer to Seattle.”

At an outdoor beach restaurant in San Diego today, a server wearing surgical gloves and a face covering rushed by with a piña colada in a pineapple-shaped cup. Another employee stood by with cleaning supplies in a gloved hand, ready to sanitize empty tables.

Customer George Cruz could only imagine what crowds may come over the weekend, when he, his wife and 6-year-old daughter will be staying home.

“That’s why we decided to come now,” he said. “There definitely will be a surplus of people at the beach.”

“I just hope everybody is smart about how they go out,” Cruz added.