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.