Peter DrakeIn Out of the Abyss, the PCs start at level 1 and "should be at least 7th level" by chapter 7. Chapters 2-6 can happen "in any order".
Isn't that a problem? Won't some encounters be lethal for a 2nd level party but trivial for a 6th level one?
Sen the Professional 
@peterdrake Knowing nothing else about it:
Yes, you'd have to change around the encounters. The rules for creating encounters are in the 5.0e Dungeon Master's Guide on p.81 - 85, so there's that, but yes it loses the convenience from being premade if you have to change around encounters by a lot.