The Florida oneway car rental deals usually take place in the fall. For this particular kind of oneway car rentals, there are no real set dates every year. It can vary by a week or two, depending on the rental volume in in the north vs the projected demand for more cars in Florida for the winter months.
That being said, those Florida one way specials tend to take place during October and November; you can start watching for the deals to be advertised by the end of August/beginning of September.
I would recommend going to some car rental company websites and signing up to receive email updates of upcoming rental car deals and one way car rental specials.
