I live near NYC and the attic fan (a small one, as the shape of the
side vent made a bigger fan of no greater benefit) made a huge
difference in attic temperature and how hot it was in the upstairs of
the house. Without it the window units I had at the time wouldn't
have been able to keep the house at a tolerable temperature.

My attic used to be probably 110 or 115 degrees, now it's roughly the
same temp as outside. It's on a thermostat and I can hear it go on
and off so I know it's working and I'm getting enough air exchange.