[This is just data - I’m sure it was “abnormally hot” in many places, but NYC was not one of those places. Believe it or not, 2000 and 1960 were just randomly picked out of a hat and the only other dates I tried fwiw]
NYC will and nearby will hold on just a little longer as all the ice water from Greenland is holding our temps down some, more in the spring, early summer but even now in early Autumn. This won't last over the years. Ice takes lots of energy to melt, but it takes much less energy to warm water beyond that.
September 1960: https://www.timeanddate.com/weather/usa/new-york/historic?mo...
September 2000: https://www.timeanddate.com/weather/usa/new-york/historic?mo...
September 2023: https://www.timeanddate.com/weather/usa/new-york/historic?mo...
2000 was a “hot” September.