Jen Philhower, 48, a part-time office manager in Austin, Texas, is one of the many Americans adjusting to almost every group activity being canceled, as people move indoors and into isolation to avoid spreading the novel coronavirus.

“My youngest goes to wilderness school, and even that is closed,” she said. “When even playing in the woods is closed, things start to feel a little strange.”

So Ms. Philhower was surprised — ecstatic, even — to see one group entertainment venue still open for business: the Blue Starlite, a local drive-in movie theater currently allowing 35 to park at one time.

Located on a hill with the Austin skyline in the background, the theater resembles a “cool junkyard,” according to Josh Frank, the owner, who opened it a decade ago. Since the virus hit the United States, the theater has screened movies including “Ferris Bueller’s Day Off” and “The Breakfast Club.”

Last Tuesday, theatergoers watched short films that were scheduled to premiere at the South by Southwest festival in Austin before it got canceled, and a feature from the festival is scheduled for later this month.

When Ms. Philhower’s children, who are 20, 16 and 12, were younger, the family would frequent the theater. The kids loved sitting on the roof of the car and chomping on candy under the stars.

“We must have seen ‘Goonies’ three times one year,” she said. But they hadn’t thought to return until they found themselves going stir crazy at home under the new public-health guidelines.

“It makes perfect sense,” Ms. Philhower said. “We can all sit in our cars, away from each other, and do something fun.”

Drive-in movie theaters may seem like a blast from the past, something out of the 1950s or ’60s. Numerous baby boomers haven’t gone for decades; Gen Xers and millennials, perhaps never.

But there are still 305 of them in the United States. according to the United Drive-In Theatre Owners Association in Stephens City, Va. The U.D.T.O.A. says every state has a drive-in movie theater except Alaska, Delaware, Hawaii, Louisiana and North Dakota.

While most drive-in theaters open for the summer, some of their owners have decided to get an early start this year to provide families an escape insulated by their cars during the pandemic, as malls, concert halls and restaurants shut down. “Who would have thought that drive-in movies would one day again become the most attractive option for going out?” Mr. Frank said.

Other owners are proceeding with caution, watching a situation that changes every day. “I think we’ve got a lucky opportunity,” said Stephen Sauerbeck, who owns Sauerbeck Family Drive-In Theater in La Grange, Ky. “But I also wonder if it’s a too-good-to-be-true kind of thing.”

Mr. Sauerbeck was correct. For the past week he has been in discussions with the governor of Kentucky and the commissioner of public health. While the option of showing movies seem to be ruled out, the state is currently allowing him to sell popcorn over the weekend and lend his venue to churches for services (patrons can sit in the car and listen to the service on their radios.)

Of course, none of that is set in stone, he said. “It seems to change every day.”

“It’s a responsibility on our side to be as safe as possible,” Mr. Sauerbeck said. “I don’t want this to be, ‘We found a loophole in the situation, and we are going to operate an underground business the government is trying to shut down.’”

‘World of Cinema’

Even before the coronavirus arrived, the drive-in movie theater business was experiencing a small renaissance.

At the end of February Mr. Frank opened a second Blue Starlite, in Round Rock, a town 25 miles north of Austin. Every weekend there have been three to five shows, all of which have sold out days in advance.

“It’s been really, really, really something,” he said. “If I had opened a Round Rock location years ago, I would be maybe three decades closer to retirement.”

Mr. Sauerbeck opened his drive-in theater in August 2018, after the last indoor theater, owned by Regal Cinemas, closed in La Grange. “2019 was such a strong summer,” he said. “‘Lion King,’ ‘Toy Story,’ ‘Spider-Man’ all performed well for us, and we grew our customers every month as long as the weather cooperated.”

The theater may look like an old dirt field, but every component of the theater is thought through. “We have no speakers or poles as some of the older ones do,” he said. “We also have a gravel parking lot so we can operate if it’s raining.”

In the recent Quentin Tarantino film “Once Upon a Time … In Hollywood,” a still-extant drive-in movie theater in Paramount, Calif., stands in for one long demolished in Van Nuys.

Spencer Folmar, a filmmaker, believes so strongly that drive-in theaters are not just the past but the future that he is building what he claims will be the world’s largest one in Eustis, Fla., with 500 spots, about a 45-minute drive from Orlando. Meant to be an immersive visual experience, it will have a lighthouse in the middle from which you can see screens in every direction.

Mr. Folmar’s goal is to provide a scene so dazzling that there is no way it could be replicated from anyone’s couch. “A cineplex can be a generic experience. You might as well stream at home,” he said. “I want to create this world of cinema with a unique design.”

Concessions by Phone

Being cooped up at home hasn’t stopped Americans from posting on Instagram and other social media platforms — indeed, it has encouraged some to step up the pace — and many drive-in theaters are trying to help provide safe and novel content.

Bailey Denise Nichols, 20, works at a dog boarding facility in Houston. When her animal clients slowed as people stopped traveling, she wanted to do so something new and different with her free time.

So she took her younger cousin to the Showboat Drive-In Theater just outside of town. They cuddled in the back seat of her car with pillows and blankets, illuminated by string light they’d brought for fun, and ate McDonald’s Chicken McNuggets they picked up on the way.

“I was surprised to find out that you use a radio frequency to listen to the movie’s audio, so that was an experience for sure,” Ms. Nichols said. “I don’t know how exactly I expected to be able to hear the movie. It’s my fault for being Generation Z, I guess.”

Last week Clay Lundquist, 43, the owner of a marketing and production company in Redmond, Wash., flew to Phoenix to watch major-league baseball spring training. When the games got canceled, he was looking for something entertaining and safe to do. “We wouldn’t have gone to a regular theater,” he said. But a drive-in theater sounded fun.

He hadn’t been to one in 20 years, and his wife, Amber Lundquist, 40, had never been.

At West Wind, an old-school establishment in Glendale, Ariz., with (now-abandoned) playgrounds and arcade games, they watched “The Invisible Man” and “The Hunt.”

People were even dancing by their cars at intermission, though there is a rule that they must stay in their car at all times except to use the restroom. “We made the choice to make the most of our time,” Mr. Lundquist said. “I do feel that if people did try a drive-in they would see the magic of the experience.”

Drive-in theaters that are open are taking extra precautions to ensure social distancing. At the Blue Starlite, you can now just flash your tickets on your phone from your window to gain admission. Many theaters have started having people order concessions by phone. Servers wearing latex gloves deliver them to the car so crowds don’t congregate in concession stands.

There are some drive-in theaters that would love to open right now but are prevented by restrictions or their worries.

After advertising on social media that it would open seven days a week while children are out of school, the Summer Quartet Drive In in Memphis was forced to close Wednesday because it is operated by Malco, and the company closed all its theaters.

Brian Francis, who runs the 99W Drive-In Theatre in Newburgh, Ore., received 30 messages from customers in the past week asking him to open early. “Folks are thinking that the drive-in is the original social distance way to see a movie, and this is some kind of golden opportunity for the vanishing drive-ins to shine,” he wrote in an email.

But Mr. Francis is hesitant to do so until he is sure Oregon won’t implement a lockdown. He is in touch with the Centers for Disease Control and Prevention, the Oregon Health Authority and his state representative, to see, “when, if, and how we can open for the 2020 season,” he said. “I want to do my part to flatten the curve.”