NEW YORK — The windowless corridor on a 20th floor in the Mott Haven Houses — a cluster of public-housing towers in the South Bronx — felt like a thoroughfare, even in the middle of a pandemic when residents are supposed to be avoiding one another.

People and their dogs poured out of the elevator, joining others in an already crowded hallway. Many residents kept their apartment doors open, allowing for a slight breeze even though the air stank of urine in some places and bleach in others.

If anyone had a face mask, they wore it around their neck.

Yet as he hung out in a stairwell holding his cane, Edgar Martinez said he believes the hardest days are still to come here.

“The summer is going to make it worse,” said Martinez, 62, who is Puerto Rican and has lived in these projects since he was 12. “These kids can’t go to the park no more. They can’t play. Imagine if you have four, five kids in your house.”

Visiting from one building over, 68-year-old Rosemary Garcia was thinking the same.

“It’s going to get real, real hot,” Garcia said, recalling how she lost two neighbors last year during a heat wave, an annual danger for the millions of Americans who live in low-income or elderly housing.

“It’s hard to worry about corona,” Martinez added, “because we are dying anyway.”

Even before the pandemic, which has killed more than 50,000 Americans, health departments in the country’s largest and most densely populated cities were nervously anticipating their battle against heat waves that sicken tens of thousands of people annually. But as summer approaches, local officials are being forced to consider how they will protect residents as the coronavirus crisis collides with the potentially deadly consequences of being poor, disabled or elderly during the hottest days of the year.

Although President Trump and some governors have called for lifting stay-at-home orders as infection rates appear to stabilize, some analysts expect it could be fall before restrictions on movement and commerce are lifted more widely — posing a potentially serious challenge to public health strategies that rely on packing people into air-conditioned places to help them survive extreme heat.

There is widespread concern among civic leaders that lifting lockdowns too soon and too drastically could spark a second wave of infection and risk overwhelming health systems again, this time in the midst of extreme weather. “It keeps me up at night,” said Deanne Criswell, New York City’s emergency management commissioner.

In many low-income city neighborhoods in the Northeast and Midwest, residents often either don’t have air conditioning or limit using it to control their electricity bills. To escape the heat, be it in a high-rise apartment in New York or a rowhouse in Baltimore, residents have traditionally gathered outdoors, at times creating difficulties for law enforcement officials trying to maintain public order.

But this year, government calls for social distancing threaten to shut down beaches, public pools, playgrounds and recreational centers, which also serve as city-run cooling centers where senior citizens can gather during heat waves and blackouts.

“This is a challenge . . . because if the order is to stay at home, then the traditional way of responding . . . is probably not feasible,” said Jeffrey Wade, executive director of the Cuyahoga Metropolitan Housing Authority in Cleveland, which serves about 55,000 residents.

In recent days, as they prepare for the next phase of the pandemic, local officials in Chicago, Baltimore, Philadelphia and New York — all cities with a history of deadly heat waves — have contemplated new strategies for addressing the looming health threat.

Though such discussions in many cities remain preliminary, officials say they are considering a range of potential solutions, including handing out free air conditioners, expanding programs that subsidize the electricity bills of low-income residents, closing streets in inner-city neighborhoods to allow people to spread out more, and expanding the number of cooling centers to keep any one location from being too crowded.

Still, some housing and social justice advocates are worried that the plans being drafted by local officials will come too late, stalling or reversing the progress many cities have made in slowing the virus’s spread.

“In the summer, it’s going to be a whole different ballgame because the culture of New York is to be outside during the summer,” said Leslie Velasquez, a program manager at El Puente, which advocates for low-income residents. “And I have yet to read or see what the plan is if we don’t want people congregating . . . when it’s too hot and uncomfortable even for them to sleep.”

Nationwide, about 87 percent of U.S. households have some form of air conditioning, according to the U.S. Energy Information Administration. But the number drops to about 80 percent for residents who live below the poverty line, the agency noted.

And in some major cities, including New York, where about 130 people die of heat-related causes every year, local officials and advocates believe that as many of as half of the units in public housing lack adequate cooling. There, the lack of air conditioning is often magnified by crowded living conditions.

Georges C. Benjamin, executive director of the American Public Health Association, said the expected reemergence of traditional summer behaviors highlights the need for guidance from public officials beyond simply asking residents to stay indoors or stay six feet apart.

“People are going to want to barbecue, and they are going to want to have large gatherings,” Benjamin said. “I think we are going to have to give them pretty good advice” on how to do it safely.

Concerns about the challenges that await big cities this summer have been heightened as public health experts increasingly signal that, unlike the flu and other viruses, the coronavirus is expected to spread throughout the warmer months.

“Now, I think the best-case scenario might be it slows down a bit, but I think we’re going to go with it straight through summer into the fall and next flu season,” said Thomas Russo, chief of the division of infectious disease at the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo.

Russo noted that the flu runs its course each year because people get vaccinated or have already been exposed — none of which applies to this new virus. And while research shows that viruses tend to linger for shorter periods in humidity — a point Trump and his health advisers have been stressing in recent days ­— Russo said he doubts summer weather alone will be enough to diminish the need for preventive measures such as social distancing and the widespread use of face masks in public.

“And you know, in the absence of air conditioning, its going to be really, really hard to wear a mask when it’s 95 [degrees] out,” Russo said. “You certainly can’t wear a mask at the swimming pool.”

Philadelphia last year released its first plan to combat the extreme heat in some neighborhoods caused by climate change and other factors. In some places, the report said, surface temperatures could be up to 22 degrees higher because of an absence of tree cover and green space, an aging housing stock and greater expanses of exposed asphalt.

The hottest neighborhoods tend to be areas with high concentrations of low-income residents, many of whom are averse to using air conditioning because of the expense or the fear it will make their homes more vulnerable to burglary.

A city program to expand the number of cooling centers and offer programming such as movies to bring in more people was supposed to launch this summer.

“Are we going to be able to operate any cooling centers or the pools?” said Christine Knapp, director of the Philadelphia Office of Sustainability. “I don’t think we know the answer to that yet.”

Even if the cooling centers can open, Philadelphia officials have begun lobbying the state to expand access to the federally funded Low Income Home Energy Assistance Program, which helps residents pay utility bills. Pennsylvania currently restricts the program to home-heating bills, Knapp said.

In Baltimore, a city with a storied history of residents hanging out on the stoops of their rowhouses, some local officials say the city needs to be even bolder in changing policies as heat-stressed residents begin flocking outdoors.

Maryland Del. Robbyn T. Lewis (D), who represents Baltimore and worked as a global health specialist before she took office, said city leaders should consider closing streets for pedestrian activity in some neighborhoods — a proposal floated in New York, too. Lewis also wants city officials to demand that Baltimore police give residents more leeway when it comes to enforcement of loitering laws.

“During the hot weather, which we know will only increase anxiety and stress, people will need an escape valve,” Lewis said. “They will need to get outside and move around.”

In Chicago, where most in the city still recall a deadly 1995 heat wave that killed more than 700 people, activists are afraid the pandemic will show the city hasn’t made enough progress in providing air conditioning to elderly or disabled residents.

A spokeswoman for the Chicago Housing Authority said all properties serving senior citizens had been updated with central heat and air, but did not respond to a question about conditions in other buildings.

Emily Coffey, a housing justice staff attorney at the Shriver Center on Poverty Law, which has tangled with the housing authority for years, noted that air conditioning is not considered an “essential” service in Chicago, meaning the utility allowance many public housing residents receive doesn’t account for that added cost.

“So, for people with low incomes, even if AC is available, that doesn’t mean they can afford to have it on,” Coffey said.

In New York City, records show that about 400,000 people live in public housing, but advocates and many city leaders believe the real figure is as high as 700,000 when unregulated crowding is accounted for.

In northern Manhattan, in the Lincoln Houses on East 135th Street, Patrice Escobar hadn’t left her apartment except to walk laps inside beside the mailboxes since the pandemic began. She’s already on medication for her anxiety, “and this is the worst type of fear ever,” she said. Occasionally, the television news catches her off-guard and she hears about how dire the situation is for senior citizens.

Her sister’s husband just died of cancer, all alone, and has been unburied for a month because of the overburdening of the funeral system. Escobar’s sister is living with her, and they’re helping each other out. But Escobar has severe allergies and her sister has asthma, so they need to keep their windows shut and the air conditioner on in the summer.

Already, she said, her air conditioner is broken.

“I’m very scared about that,” she said. “The weather’s going to warm soon, and due to my breathing and my sister’s asthma, that’s going to be difficult.”

Ritchie Torres, a city council member and Democratic congressional candidate from the Bronx who grew up in public housing, said an immediate solution to the problem may be a massive city-run program to buy air conditioners, or a request that major manufacturers donate them for residents in both New York City Housing Authority units and cramped low-income private housing.

“It’s a matter of public health, a matter of life and death,” Torres said.

But New York City is already facing a multibillion-dollar budget deficit because of the pandemic. Criswell, the city’s emergency management commissioner, said officials will “do whatever it takes to support New Yorkers and make sure they’re safe.” But as officials find their way to imperfect solutions in the new world order, she encouraged residents to keep windows open and to take cold showers.

At the Queensbridge Houses in Long Island City — the largest housing project in North America, with 26 buildings — some residents were mentally preparing to follow such advice, albeit with personalized heat-busting strategies they honed long before the coronavirus arrived.

“If the ACs don’t work, I put ice water in my window and hope that’ll blow in the good breeze,” said Michael Johnson, 23, who expects he’ll be hanging out around home even more than usual this summer — he was recently laid off because of the pandemic.

Craig reported from Washington. Bailey reported from Milwaukee.