I don't know what to make of this but I'm just going to put it out there: I live in Bergen county, NJ right on the other side of the West Hudson from Manhattan and for maybe the past three days and nights there have been non-stop helicopters flying over my head. As far as I can tell (not an expert) they look non-military. About half the time I can hear two at once. Was up at 4am and they were still there.
Anyone else in the area? Anyone know of a reason?
edit: 10:41am just at least four helicopters heading south along Hudson. These were military.
You could check out https://globe.adsbexchange.com/ and look up what type of heli's they are.
If they look to have some weird nose attachments they could be sniffers (heli's equipped to sample the air to detect weapons (bio/chem/nuke) etc.