Lore question

The Harrowing comes from the shadow Isles onto the mainland, bringing with it the legions of the dead to terrorize and cull the living. its like Mardi gras :D

edit: http://www.surrenderat20.net/2015/10/shadow-and-fortune_27.html this is the most recent harrowing event set in bilgewater

Harrowing used to be a Halloween thing. This past year they stated that since the Harrowing in actuality can happen at any time in Runeterra (thus why everyone doesn't just move to their vacation house when Harrowing would near on the calendar in Bilgewater). So, we can now get a Harrowing story at any time Riot wants, since they aren't locked into October any more.