A NYC subway car without AC when it's 87 degrees outside is worse than 100° in Florida; Florida is a lot more effective AC, pools/lanais, open spaces.
Does that really exist in 2021? (Or even 2001?) I doubt the driver's union would allow it. It would be unsafe.
In NYC, you’re almost certainly in an older, smaller building and likely have lousy HVAC. The subway is great, but in many stations you learn to love the unique aroma of garbage juice mixed with hot piss that tends to be a thing.
In a Florida summer, the outdoors is a swamp, but you don't have to spend much time there. The whole place is built for cars; you can (if you wish) go straight from building A, to your car, to building B. Presuming underground parking, you might never even touch non-air-conditioned air.
In an NYC summer, meanwhile, in many buildings, the indoors is the swamp. (And often their attached yards / alleyways as well, if they're enclosed around by tall buildings.)
In NYC it may be a little cooler, but your exposure to the elements is constant. You walk to the train, lunch, coffee, dinner, groceries, etc out on the sweaty sidewalk.
When it's 90F, the train station might be 100F and train at best 80F though often much higher.
You can live in a $2-3 million apartment yet have a lobby not be air conditioned, nor the hallways or elevator. No one has pools. You can go down to the park by the rivers, but you aren't going in for a swim. All the concrete & asphalt absorb and radiate the heat.
I'd go down to FL in summer since if it's going to be 90F+ and humid, I'd rather be able to jump in the ocean or a pool.
Not saying those things are in NYC, there's many other great cities, but I definitely wouldn't pick a place just for the weather.
I've spent time in the mid-Atlantic region and time in South Florida. Miami in July is the closest thing to hell on Earth. But I'd rather deal with that and live in a beautiful climate year-round than deal with north eastern winters.
Thank goodness the West Coast exists to relieve us of that dreadful dilemma!