Since the beginning of the week, temperatures have hovered in the mid-90s or higher during the daytime. And night brings little respite, with the heat staying largely trapped by the asphalt.
At least one death in New York has been attributed to the extreme weather, which started earlier in the month: a 57-year-old man perished in Staten Island on July 8.
The city is under an "excessive heat warning," and officials are urging everyone to take precautions.
More than 420 cooling centres -- typically air conditioned libraries or community centres -- have been opened for those in need, especially senior citizens, authorities emphasised.
New Yorkers are being told to drink up -- water, not alcohol or soda -- and stay inside until the brutal heat dissipates.
That's expected to happen this weekend, after a storm meteorologists warn could be violent.
Meanwhile, in the white hot city streets, residents and visitors are making do as best they can.
In some buildings, janitors distributed small bottles of water to residents.
One pedestrian fanned herself with a peacock feather. And in Union Square, chess players tried to create a patch of shade with umbrellas and parasols brought from home.
Humour was the order of the day at a Lutheran church in the city, which posted a sign outside saying, "The devil called. He wants his weather back."
The entire north-east is affected.
