How long does it rain in New York?

I have been trying to find a reliable source on rainfall in New York, but everything I find is in yearly averages and all sorts of stuff I don’t care about.
Long story, short: I am writing a book that takes place in New York. I am painfully anal about my details and having never visited New York for an extended period of time, do not know how long it usually rains there, near the Harriman State Park during the late summer, nearing the fall session.
I know this detail is meaningless, in most part, but I have a disorder.