Just a couple of months ago I was the only person on a US 737 from BWI to CLT. One of the tropical storms, I don't remember which, was working its way up the coast and things were a mess. I was supposed to go to PIT - the flight was cancelled and they routed me via CLT on a flight that was running a few hours late. I can't imagine there were no scheduled pax - maybe they found other ways to CLT earlier.
It was just me, two FA's and two in the cockpit. Plus a fabulous light show all the way down the coast. I still have pictures on my phone of a completely empty cabin.