Around 90 percent of New York homes have air conditioning, according to city data.
On paper, that sounds like a city that has beaten the summer for good.
Then a record heat wave rolled in, and when it lifted, 19 people had lost their lives to heat stress.
The detail that showed up in case after case was not what most people expected.
It had nothing to do with being outdoors, and nothing to do with the power grid going dark.
It had everything to do with what was inside people’s homes, and what was not.
A city that thought it had solved summer
New York is not a city without cooling.
That near universal air conditioning felt, for generations, like the end of the story.
Summers conquered, danger managed, the heat reduced to a minor inconvenience.
But heat is now the most dangerous weather New York City faces, and climate change is making dangerously hot weather more frequent and intense.
In mid-May 2025, the city was already under its earliest heat advisory on record.
The machine in the window was never the whole answer.
When the AC is there but the danger isn’t gone
Here is the part of the story that does not make the weather forecast.
Among those who lost their lives to heat stress and whose home cooling status could be confirmed, not one had a working air conditioner in use at the time, according to New York City Health Department records.
Owning a unit and running it are two entirely different things.
Not everyone can afford to run them continuously, raising the chances of heat stress and even life-threatening illness, especially for older residents and people with cardiovascular or other underlying conditions.
The heat does not check your energy bill before it decides to hurt you.
Rising electricity costs have turned a life-saving machine into a financial calculation millions of Americans make every sweltering night.
The city that bakes before the sun goes down
There is another force working against anyone trying to stay cool, and it lives in the streets themselves.
New York carries its own version of the urban heat island burden.
A 2024 Climate Central analysis found that New York City’s built environment makes temperatures an average of nearly 10 degrees Fahrenheit hotter for the average resident than they would otherwise be, the largest per capita urban heat island effect measured among the 65 major U.S. cities studied.
Some neighborhoods feel even more: parts of the city register heat indexes more than 12 degrees above what nature alone would produce.
Without AC, indoor temperatures can climb far higher than the temperature outside, especially at night, and can stay elevated for days after a heat wave passes.
The apartment does not cool down just because the sun sets.
The concrete and asphalt absorbed the heat all day and are slowly giving it back, hour by hour, through the wall and the floor.
The 19, and the thing they shared
Officials linked the spike in cases to the June 2025 heat wave, and all but three were Black or Latino, with many at home without air conditioning.
The NYC Health Department’s 2026 report confirmed the pattern that had been building for years.
Most people who lost their lives to heat stress were exposed to dangerous temperatures in homes without air conditioning.
Lack of access to cooling equipment and affordable energy to operate it remains one of the most significant risk factors for heat-related harm.
The program meant to help run out of funding on June 5, earlier than any previous year, leaving thousands unable to access life-saving home cooling.
The city’s 2026 heat-related health report makes clear this is not a crisis that appeared overnight: around 500 New Yorkers lose their lives to heat-related causes each year.
And the thermostat settings most people rely on were never designed for nights that simply refuse to cool down, a lesson that has played out in coastal cities chasing the same moving target.
What comes after the window unit
The answer emerging from cities across the country is not simply more air conditioning.
It is rethinking the building, the block and the whole neighborhood as a living system.
Some architects are using passive house standards when building and retrofitting homes, prioritizing airtightness and insulation to hold a comfortable temperature without constant mechanical cooling.
Trees, reflective rooftops and green corridors do the same work without drawing a single watt.
Research on urban heat islands consistently shows that neighborhoods with little tree canopy and more heat-absorbing surfaces can run significantly hotter than greener areas just blocks away, a gap driven almost entirely by the presence or absence of shade and vegetation.
Extreme heat already claims more American lives each year than floods, tornadoes and hurricanes combined.
That is not a forecast for some distant future.
It is the number from last summer, ticking upward in cities that still believe the answer hums in a box bolted to the window.
The box helps. But the city around it has to change too.