As mentioned. It depends on where you are. A NP campground states you can't run them during quiet hours. No matter how hot it is, or how quiet you think your generator is.
I do know that in the NP CGs on the Blue Ridge Park way. There is no such thing as a "quiet" generator. In the stillness that is the BRP, you can hear a lantern burning a football field away. So your internal combustion engine is quite the noise maker.
IMOP. IF you just got to have electricity, and you are not out somewhere all alone. You need to stay in a Cg that has hookups.