Here's a quote from you:
Actually, November is a very active month in those areas, as many celebrations are held in coincidence with the end of the harvest season.
In particular, a celebration is held for the death of Smaug (Dragontide, early November, Esgaroth) and one for the victory at the Battle of Five Armies (Gathering of Five Armies, late November, Dale). Dragontide is detailed in the upcoming Lake-town book, while one Gathering is the object of one adventure in Tales from Wilderland. Sorry to be a tease!
So, references about the Gathering being in Esgaroth or in Summer were in error (Gloin's fault, obviously!.
Francesco