The rain part is very understandable, but Lolla is rain or shine. It actually made for some pretty gnarly sets last year on Sunday. We had a downpour around 4:00 PM or so and then later around 8:00 PM right before or during the final acts. Look up footage on YouTube of Cage the Elephant, Foo Fighters, Cold War Kids, or Deadmau5 from last year and you can see what I mean.
And most of the acts get a forty-five minute to an hour slot too so it makes for a pretty satisfying set time. The past two years I've seen my favorite bands play everything I'd want to hear from them.
They are your favorite band and you can hear everything you want in 45 minutes? That doesn't even really make sense...
the festival slot time is great for bands you know some of their popular songs but aren't really into enough to sit through a two hour set. but you still need a bunch of those to show up to make it worth going.