Averaging over the years September is typically amazing because of the infusion of bunker, the availability of small inshore tuna family species, the thick bodied summer fat rich stripers and blues, and the cooling trend livening up dead zones.
Each year is different and this year tends to be cooler thus the excellent action we're having now in what is normally the dog days. I don't think that will affect fall fishing.
I get wanderlust for greased line fishing for summer steelhead out in the pacific northwest around that time, but the cape fishing is definitely good in September.
I can tell you it's good now - I haven't caught a schoolie for days, every fish is taking 50-100 yards of backing.
IFFF Certified THCI @ 2005
Capeflyfisher Guide Service
Island Hopper, Guitarist, Incurable Dreamer
and Founder, Worldwide Flyfishing Forum